refactor(nexus): mount new frame in Layout.tsx; kill old chrome (phase 8)

Rewrites Layout.tsx to compose the new Phase 8 frame (IconRail +
TopStrip) and remove the old chrome elements specified as killed in
docs/specs/2026-04-11-nexus-layout-overhaul.md §2:

Removed from chrome:
  - 280px collapsible Sidebar / InstanceSidebar
  - ChatPanel global slide-in right rail
  - PropertiesPanel global slide-in right rail
  - BreadcrumbBar (replaced by ModeBreadcrumb inside TopStrip)
  - Footer row with Docs link, version tooltip, instance settings button,
    chat toggle button, theme toggle button
  - Effect that closed PropertiesPanel when chat opened
  - Mobile sidebar drawer block
  - Mobile sidebar swipe gesture listener

Preserved:
  - Company-prefix URL sync and fallback redirect machinery
  - First-run onboarding trigger
  - WorktreeBanner, DevRestartBanner
  - Scroll-based mobile nav visibility tracking
  - Body overflow management
  - Instance settings path memory
  - Dialog overlays (NewIssue, NewProject, NewGoal, NewAgent)
  - ToastViewport, CommandPalette
  - MobileBottomNav (mobile only; Phase 15 replaces)

Added:
  - IconRail mount with derived companyPrefix from matchedCompany or
    selectedCompany
  - TopStrip mount above the main content area
  - hasUnknownCompanyPrefix fallback defaults to /assistant instead of
    /dashboard (Dashboard is killed in the new IA)
  - useKeyboardShortcuts.onSearch dispatches the same synthetic Meta+K
    keydown as the CmdKButton shim

The Sidebar, InstanceSidebar, BreadcrumbBar, ChatPanel, PropertiesPanel,
ThemeContext, and useChatPanel files remain in the repo; Phase 16
deletes dead files after the other Phase 8 tasks are proven stable.

Pages render unchanged in the new frame and will look visually wrong
until Phases 9-13 rebuild their internals. That is the expected
intermediate state per the spec.

Part of Phase 8 of the Nexus layout overhaul (task 6 of 7).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -1,14 +1,8 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import { useQuery } from "@tanstack/react-query";
-import { BookOpen, MessageSquare, Moon, Settings, Sun } from "lucide-react";
-import { Link, Navigate, Outlet, useLocation, useNavigate, useParams } from "@/lib/router";
+import { Navigate, Outlet, useLocation, useNavigate, useParams } from "@/lib/router";
 // [nexus] CompanyRail intentionally not rendered — single-workspace mode.
 // The file is preserved for upstream rebase compatibility.
-import { Sidebar } from "./Sidebar";
-import { InstanceSidebar } from "./InstanceSidebar";
-import { BreadcrumbBar } from "./BreadcrumbBar";
-import { ChatPanel } from "./ChatPanel";
-import { PropertiesPanel } from "./PropertiesPanel";
 import { CommandPalette } from "./CommandPalette";
 import { NewIssueDialog } from "./NewIssueDialog";
 import { NewProjectDialog } from "./NewProjectDialog";
@@ -18,13 +12,12 @@ import { ToastViewport } from "./ToastViewport";
 import { MobileBottomNav } from "./MobileBottomNav";
 import { WorktreeBanner } from "./WorktreeBanner";
 import { DevRestartBanner } from "./DevRestartBanner";
+import { IconRail } from "./frame/IconRail";
+import { TopStrip } from "./frame/TopStrip";
 import { useDialog } from "../context/DialogContext";
 import { GeneralSettingsProvider } from "../context/GeneralSettingsContext";
-import { usePanel } from "../context/PanelContext";
-import { useChatPanel } from "../context/ChatPanelContext";
 import { useCompany } from "../context/CompanyContext";
 import { useSidebar } from "../context/SidebarContext";
-import { useTheme } from "../context/ThemeContext";
 import { useKeyboardShortcuts } from "../hooks/useKeyboardShortcuts";
 import { useCompanyPageMemory } from "../hooks/useCompanyPageMemory";
 import { healthApi } from "../api/health";
@@ -37,8 +30,6 @@ import {
 import { queryKeys } from "../lib/queryKeys";
 import { cn } from "../lib/utils";
 import { NotFoundPage } from "../pages/NotFound";
-import { Button } from "@/components/ui/button";
-import { Tooltip, TooltipTrigger, TooltipContent } from "@/components/ui/tooltip";
 
 const INSTANCE_SETTINGS_MEMORY_KEY = "paperclip.lastInstanceSettingsPath";
 
@@ -52,10 +43,8 @@ function readRememberedInstanceSettingsPath(): string {
 }
 
 export function Layout() {
-  const { sidebarOpen, setSidebarOpen, toggleSidebar, isMobile } = useSidebar();
+  const { isMobile } = useSidebar();
   const { openNewIssue, openOnboarding } = useDialog();
-  const { togglePanelVisible, setPanelVisible } = usePanel();
-  const { chatOpen, setChatOpen, toggleChat } = useChatPanel();
   const {
     companies,
     loading: companiesLoading,
@@ -64,17 +53,14 @@ export function Layout() {
     selectionSource,
     setSelectedCompanyId,
   } = useCompany();
-  const { theme, toggleTheme } = useTheme();
-  const isDarkTheme = theme === "dark";
-  const nextThemeLabel = isDarkTheme ? "Light" : "Dark";
   const { companyPrefix } = useParams<{ companyPrefix: string }>();
   const navigate = useNavigate();
   const location = useLocation();
-  const isInstanceSettingsRoute = location.pathname.startsWith("/instance/");
   const onboardingTriggered = useRef(false);
   const lastMainScrollTop = useRef(0);
   const [mobileNavVisible, setMobileNavVisible] = useState(true);
-  const [instanceSettingsTarget, setInstanceSettingsTarget] = useState<string>(() => readRememberedInstanceSettingsPath());
+  const [, setInstanceSettingsTarget] = useState<string>(() => readRememberedInstanceSettingsPath());
+
   const matchedCompany = useMemo(() => {
     if (!companyPrefix) return null;
     const requestedPrefix = companyPrefix.toUpperCase();
@@ -82,6 +68,9 @@ export function Layout() {
   }, [companies, companyPrefix]);
   const hasUnknownCompanyPrefix =
     Boolean(companyPrefix) && !companiesLoading && companies.length > 0 && !matchedCompany;
+
+  const railCompanyPrefix = matchedCompany?.issuePrefix ?? selectedCompany?.issuePrefix ?? null;
+
   const { data: health } = useQuery({
     queryKey: queryKeys.health,
     queryFn: () => healthApi.get(),
@@ -97,16 +86,9 @@ export function Layout() {
     queryFn: () => instanceSettingsApi.getGeneral(),
   }).data?.keyboardShortcuts === true;
 
-  // [nexus] Removed the `health?.deploymentMode === "authenticated"` gate.
-  // Paperclip's upstream assumed authenticated mode = hosted multi-tenant where
-  // users self-onboard via invites, so the first-run wizard was suppressed.
-  // Nexus's authenticated mode is single-user LAN (BETTER_AUTH), which still
-  // needs the first-run wizard. Note: this effect is mostly dead code for the
-  // zero-company case because CompanyRootRedirect navigates to /onboarding
-  // before Layout ever mounts — the real auto-open trigger lives in
-  // OnboardingRoutePage (App.tsx). This effect is retained as a belt-and-
-  // suspenders fallback for edge cases where a user reaches a Layout-mounted
-  // route with zero companies (e.g. /instance/settings/*).
+  // [nexus] First-run onboarding trigger. Retained as a belt-and-suspenders
+  // fallback for edge cases where a user reaches a Layout-mounted route with
+  // zero companies (e.g. /instance/settings/*).
   useEffect(() => {
     if (companiesLoading || onboardingTriggered.current) return;
     if (companies.length === 0) {
@@ -115,6 +97,7 @@ export function Layout() {
     }
   }, [companies, companiesLoading, openOnboarding]);
 
+  // Company-prefix URL sync.
   useEffect(() => {
     if (!companyPrefix || companiesLoading || companies.length === 0) return;
 
@@ -156,25 +139,22 @@ export function Layout() {
     setSelectedCompanyId,
   ]);
 
-  const togglePanel = togglePanelVisible;
-
-  // Close PropertiesPanel when chat panel opens
-  useEffect(() => {
-    if (chatOpen) {
-      setPanelVisible(false);
-    }
-  }, [chatOpen, setPanelVisible]);
-
   useCompanyPageMemory();
 
   useKeyboardShortcuts({
     enabled: keyboardShortcutsEnabled,
     onNewIssue: () => openNewIssue(),
-    onToggleSidebar: toggleSidebar,
-    onTogglePanel: togglePanel,
+    onToggleSidebar: () => {
+      // Phase 8: sidebar toggle is a no-op from keyboard — the rail is fixed.
+      // Kept as a stub so useKeyboardShortcuts' type contract is satisfied.
+    },
+    onTogglePanel: () => {
+      // Phase 8: PropertiesPanel is no longer mounted globally.
+    },
     onSearch: () => {
-      if (!chatOpen) setChatOpen(true);
-      requestAnimationFrame(() => window.dispatchEvent(new Event("nexus:focus-chat-search")));
+      // Phase 8: open the command palette via synthetic keydown, mirroring
+      // the CmdKButton shim. Phase 14 replaces with a real palette context.
+      document.dispatchEvent(new KeyboardEvent("keydown", { key: "k", metaKey: true, bubbles: true }));
     },
   });
 
@@ -187,62 +167,11 @@ export function Layout() {
     setMobileNavVisible(true);
   }, [isMobile]);
 
-  // Swipe gesture to open/close sidebar on mobile
-  useEffect(() => {
-    if (!isMobile) return;
-
-    const EDGE_ZONE = 30; // px from left edge to start open-swipe
-    const MIN_DISTANCE = 50; // minimum horizontal swipe distance
-    const MAX_VERTICAL = 75; // max vertical drift before we ignore
-
-    let startX = 0;
-    let startY = 0;
-
-    const onTouchStart = (e: TouchEvent) => {
-      const t = e.touches[0]!;
-      startX = t.clientX;
-      startY = t.clientY;
-    };
-
-    const onTouchEnd = (e: TouchEvent) => {
-      const t = e.changedTouches[0]!;
-      const dx = t.clientX - startX;
-      const dy = Math.abs(t.clientY - startY);
-
-      if (dy > MAX_VERTICAL) return; // vertical scroll, ignore
-
-      // Swipe right from left edge → open
-      if (!sidebarOpen && startX < EDGE_ZONE && dx > MIN_DISTANCE) {
-        setSidebarOpen(true);
-        return;
-      }
-
-      // Swipe left when open → close
-      if (sidebarOpen && dx < -MIN_DISTANCE) {
-        setSidebarOpen(false);
-      }
-    };
-
-    document.addEventListener("touchstart", onTouchStart, { passive: true });
-    document.addEventListener("touchend", onTouchEnd, { passive: true });
-
-    return () => {
-      document.removeEventListener("touchstart", onTouchStart);
-      document.removeEventListener("touchend", onTouchEnd);
-    };
-  }, [isMobile, sidebarOpen, setSidebarOpen]);
-
   const updateMobileNavVisibility = useCallback((currentTop: number) => {
     const delta = currentTop - lastMainScrollTop.current;
-
-    if (currentTop <= 24) {
-      setMobileNavVisible(true);
-    } else if (delta > 8) {
-      setMobileNavVisible(false);
-    } else if (delta < -8) {
-      setMobileNavVisible(true);
-    }
-
+    if (currentTop <= 24) setMobileNavVisible(true);
+    else if (delta > 8) setMobileNavVisible(false);
+    else if (delta < -8) setMobileNavVisible(true);
     lastMainScrollTop.current = currentTop;
   }, []);
 
@@ -252,24 +181,17 @@ export function Layout() {
       lastMainScrollTop.current = 0;
       return;
     }
-
     const onScroll = () => {
       updateMobileNavVisibility(window.scrollY || document.documentElement.scrollTop || 0);
     };
-
     onScroll();
     window.addEventListener("scroll", onScroll, { passive: true });
-
-    return () => {
-      window.removeEventListener("scroll", onScroll);
-    };
+    return () => window.removeEventListener("scroll", onScroll);
   }, [isMobile, updateMobileNavVisibility]);
 
   useEffect(() => {
     const previousOverflow = document.body.style.overflow;
-
     document.body.style.overflow = isMobile ? "visible" : "hidden";
-
     return () => {
       document.body.style.overflow = previousOverflow;
     };
@@ -277,12 +199,10 @@ export function Layout() {
 
   useEffect(() => {
     if (!location.pathname.startsWith("/instance/settings/")) return;
-
     const nextPath = normalizeRememberedInstanceSettingsPath(
       `${location.pathname}${location.search}${location.hash}`,
     );
     setInstanceSettingsTarget(nextPath);
-
     try {
       window.localStorage.setItem(INSTANCE_SETTINGS_MEMORY_KEY, nextPath);
     } catch {
@@ -293,183 +213,36 @@ export function Layout() {
   return (
     <GeneralSettingsProvider value={{ keyboardShortcutsEnabled }}>
       <div
-      className={cn(
-        "bg-background text-foreground pt-[env(safe-area-inset-top)]",
-        isMobile ? "min-h-dvh" : "flex h-dvh flex-col overflow-hidden",
-      )}
-      >
-      <a
-        href="#main-content"
-        className="sr-only focus:not-sr-only focus:fixed focus:left-3 focus:top-3 focus:z-[200] focus:rounded-md focus:bg-background focus:px-3 focus:py-2 focus:text-sm focus:font-medium focus:shadow-lg focus:outline-none focus-visible:ring-2 focus-visible:ring-ring"
-      >
-        Skip to Main Content
-      </a>
-      <WorktreeBanner />
-      <DevRestartBanner devServer={health?.devServer} />
-      <div className={cn("min-h-0 flex-1", isMobile ? "w-full" : "flex overflow-hidden")}>
-        {isMobile && sidebarOpen && (
-          <button
-            type="button"
-            className="fixed inset-0 z-40 bg-black/50"
-            onClick={() => setSidebarOpen(false)}
-            aria-label="Close sidebar"
-          />
+        className={cn(
+          "bg-background text-foreground pt-[env(safe-area-inset-top)]",
+          isMobile ? "min-h-dvh" : "flex h-dvh flex-col overflow-hidden",
         )}
+      >
+        <a
+          href="#main-content"
+          className="sr-only focus:not-sr-only focus:fixed focus:left-3 focus:top-3 focus:z-[200] focus:rounded-md focus:bg-background focus:px-3 focus:py-2 focus:text-sm focus:font-medium focus:shadow-lg focus:outline-none focus-visible:ring-2 focus-visible:ring-ring"
+        >
+          Skip to Main Content
+        </a>
 
-        {isMobile ? (
-          <div
-            className={cn(
-              "fixed inset-y-0 left-0 z-50 flex flex-col overflow-hidden pt-[env(safe-area-inset-top)] transition-transform duration-100 ease-out",
-              sidebarOpen ? "translate-x-0" : "-translate-x-full"
-            )}
-          >
-            <div className="flex flex-1 min-h-0 overflow-hidden">
-              {isInstanceSettingsRoute ? <InstanceSidebar /> : <Sidebar />}
-            </div>
-            <div className="border-t border-r border-border px-3 py-2 bg-background">
-              <div className="flex items-center gap-1">
-                <a
-                  href="https://docs.paperclip.ing/"
-                  target="_blank"
-                  rel="noopener noreferrer"
-                  className="flex items-center gap-2.5 px-3 py-2 text-[13px] font-medium transition-colors text-foreground/80 hover:bg-accent/50 hover:text-foreground flex-1 min-w-0"
-                >
-                  <BookOpen className="h-4 w-4 shrink-0" />
-                  <span className="truncate">Documentation</span>
-                </a>
-                {health?.version && (
-                  <Tooltip>
-                    <TooltipTrigger asChild>
-                      <span className="px-2 text-xs text-muted-foreground shrink-0 cursor-default">v</span>
-                    </TooltipTrigger>
-                    <TooltipContent>v{health.version}</TooltipContent>
-                  </Tooltip>
-                )}
-                <Button variant="ghost" size="icon-sm" className="text-muted-foreground shrink-0" asChild>
-                  <Link
-                    to={instanceSettingsTarget}
-                    aria-label="Instance settings"
-                    title="Instance settings"
-                    onClick={() => {
-                      if (isMobile) setSidebarOpen(false);
-                    }}
-                  >
-                    <Settings className="h-4 w-4" />
-                  </Link>
-                </Button>
-                <Button
-                  type="button"
-                  variant="ghost"
-                  size="icon-sm"
-                  className="text-muted-foreground shrink-0"
-                  onClick={toggleTheme}
-                  aria-label={`Switch to ${nextThemeLabel}`}
-                  title={`Switch to ${nextThemeLabel}`}
-                >
-                  {isDarkTheme ? <Sun className="h-4 w-4" /> : <Moon className="h-4 w-4" />}
-                </Button>
-              </div>
-            </div>
-          </div>
-        ) : (
-          <div className="flex h-full flex-col shrink-0">
-            <div className="flex flex-1 min-h-0">
-              <div
-                className={cn(
-                  "overflow-hidden transition-[width] duration-100 ease-out",
-                  sidebarOpen ? "w-60" : "w-0"
-                )}
-              >
-                {isInstanceSettingsRoute ? <InstanceSidebar /> : <Sidebar />}
-              </div>
-            </div>
-            <div className="border-t border-r border-border px-3 py-2">
-              <div className="flex items-center gap-1">
-                <a
-                  href="https://docs.paperclip.ing/"
-                  target="_blank"
-                  rel="noopener noreferrer"
-                  className="flex items-center gap-2.5 px-3 py-2 text-[13px] font-medium transition-colors text-foreground/80 hover:bg-accent/50 hover:text-foreground flex-1 min-w-0"
-                >
-                  <BookOpen className="h-4 w-4 shrink-0" />
-                  <span className="truncate">Documentation</span>
-                </a>
-                {health?.version && (
-                  <Tooltip>
-                    <TooltipTrigger asChild>
-                      <span className="px-2 text-xs text-muted-foreground shrink-0 cursor-default">v</span>
-                    </TooltipTrigger>
-                    <TooltipContent>v{health.version}</TooltipContent>
-                  </Tooltip>
-                )}
-                <Button variant="ghost" size="icon-sm" className="text-muted-foreground shrink-0" asChild>
-                  <Link
-                    to={instanceSettingsTarget}
-                    aria-label="Instance settings"
-                    title="Instance settings"
-                    onClick={() => {
-                      if (isMobile) setSidebarOpen(false);
-                    }}
-                  >
-                    <Settings className="h-4 w-4" />
-                  </Link>
-                </Button>
-                <Tooltip>
-                  <TooltipTrigger asChild>
-                    <Button
-                      type="button"
-                      variant="ghost"
-                      size="icon-sm"
-                      className="hidden md:inline-flex text-muted-foreground shrink-0"
-                      onClick={toggleChat}
-                      aria-label={chatOpen ? "Close chat" : "Open chat"}
-                    >
-                      <MessageSquare className="h-4 w-4" />
-                    </Button>
-                  </TooltipTrigger>
-                  <TooltipContent>{chatOpen ? "Close chat" : "Open chat"}</TooltipContent>
-                </Tooltip>
-                <Button
-                  type="button"
-                  variant="ghost"
-                  size="icon-sm"
-                  className="text-muted-foreground shrink-0"
-                  onClick={toggleTheme}
-                  aria-label={`Switch to ${nextThemeLabel}`}
-                  title={`Switch to ${nextThemeLabel}`}
-                >
-                  {isDarkTheme ? <Sun className="h-4 w-4" /> : <Moon className="h-4 w-4" />}
-                </Button>
-              </div>
-            </div>
-          </div>
-        )}
+        <WorktreeBanner />
+        <DevRestartBanner devServer={health?.devServer} />
+
+        <div className={cn("min-h-0 flex-1", isMobile ? "w-full" : "flex overflow-hidden")}>
+          <IconRail companyPrefix={railCompanyPrefix} />
+
+          <div className={cn("flex min-w-0 flex-col", isMobile ? "w-full" : "h-full flex-1")}>
+            <TopStrip />
 
-        <div className={cn("flex min-w-0 flex-col", isMobile ? "w-full" : "h-full flex-1")}>
-          <div
-            className={cn(
-              isMobile && "sticky top-0 z-20 bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/85",
-            )}
-          >
-            <BreadcrumbBar />
-          </div>
-          <div className={cn(isMobile ? "block" : "flex flex-1 min-h-0")}>
             <main
               id="main-content"
               tabIndex={-1}
               className={cn(
-                "flex-1 p-4 md:p-6",
-                isMobile ? "overflow-visible pb-[calc(5rem+env(safe-area-inset-bottom))]" : "overflow-auto",
+                "flex-1",
+                isMobile ? "overflow-visible pb-[calc(5rem+env(safe-area-inset-bottom))]" : "overflow-auto p-4 md:p-6",
               )}
             >
               {hasUnknownCompanyPrefix ? (
-                // [nexus] Auto-recover from bogus URL prefixes by redirecting
-                // to the same path under the first available company, instead
-                // of leaving the user stranded on an "Invite not available"
-                // style dead end with no way back. hasUnknownCompanyPrefix is
-                // already gated on companies.length > 0, so the fallback is
-                // guaranteed to resolve. If no fallback exists for some reason,
-                // fall through to the old NotFoundPage.
                 (() => {
                   const fallbackCompany = selectedCompany ?? companies[0] ?? null;
                   if (!fallbackCompany) {
@@ -480,7 +253,7 @@ export function Layout() {
                       />
                     );
                   }
-                  const restOfPath = location.pathname.replace(/^\/[^/]+/, "") || "/dashboard";
+                  const restOfPath = location.pathname.replace(/^\/[^/]+/, "") || "/assistant";
                   return (
                     <Navigate
                       to={`/${fallbackCompany.issuePrefix}${restOfPath}${location.search}${location.hash}`}
@@ -492,18 +265,17 @@ export function Layout() {
                 <Outlet />
               )}
             </main>
-            <ChatPanel />
-            <PropertiesPanel />
           </div>
         </div>
-      </div>
-      {isMobile && <MobileBottomNav visible={mobileNavVisible} />}
-      <CommandPalette />
-      <NewIssueDialog />
-      <NewProjectDialog />
-      <NewGoalDialog />
-      <NewAgentDialog />
-      <ToastViewport />
+
+        {isMobile && <MobileBottomNav visible={mobileNavVisible} />}
+
+        <CommandPalette />
+        <NewIssueDialog />
+        <NewProjectDialog />
+        <NewGoalDialog />
+        <NewAgentDialog />
+        <ToastViewport />
       </div>
     </GeneralSettingsProvider>
   );