[nexus] feat(19-03): dual-section Installed tab and read-only SkillCard for native skills

- SkillCard: add isReadOnly and source props; hide update/rollback/install when isReadOnly
- SkillCard: show Native badge when isReadOnly or source=native
- SkillBrowser: remove agentSkillsDir state and text input from install dialog
- SkillBrowser: add selectedAgentId state for per-agent installed skills view
- SkillBrowser: add agentInstalledSkills query using skillGroupsApi.listAgentSkills
- SkillBrowser: split installed skills into managedSkills/nativeSkills sections
- SkillBrowser: render Managed/Native section headings when nativeSkills.length > 0
- SkillBrowser: uninstall dialog now carries agentId and calls skillRegistryApi.uninstall
- SkillBrowser: install dialog sends agentId directly (no agentSkillsDir text input)

ui/src/components/SkillCard.tsx

@@ -20,6 +20,8 @@ export interface SkillCardProps {
   onRollback?: () => void;
   onUninstall?: () => void;
   isLoading?: boolean;
+  isReadOnly?: boolean;
+  source?: "managed" | "native";
   className?: string;
 }
 
@@ -32,13 +34,15 @@ export function SkillCard({
   onRollback,
   onUninstall,
   isLoading = false,
+  isReadOnly = false,
+  source,
   className,
 }: SkillCardProps) {
   return (
     <Card className={cn("flex flex-col", className)}>
       <CardContent className="p-4 flex flex-col gap-2">
 
-        {/* Row 1: name link (primary visual anchor) + update badge */}
+        {/* Row 1: name link (primary visual anchor) + update badge + native badge */}
         <div className="flex items-start justify-between gap-2">
           <Link
             to={`/skills/detail/${encodeURIComponent(skill.id)}`}
@@ -46,15 +50,26 @@ export function SkillCard({
           >
             {skill.name}
           </Link>
-          {hasUpdate && (
-            <Badge
-              variant="outline"
-              className="text-xs text-amber-600 border-amber-500 shrink-0"
-              aria-label="Update available"
-            >
-              Update
-            </Badge>
-          )}
+          <div className="flex shrink-0 gap-1">
+            {(isReadOnly || source === "native") && (
+              <Badge
+                variant="secondary"
+                className="text-xs text-muted-foreground"
+                aria-label="Native skill"
+              >
+                Native
+              </Badge>
+            )}
+            {hasUpdate && !isReadOnly && (
+              <Badge
+                variant="outline"
+                className="text-xs text-amber-600 border-amber-500"
+                aria-label="Update available"
+              >
+                Update
+              </Badge>
+            )}
+          </div>
         </div>
 
         {/* Row 2: description (2-line clamp) */}
@@ -72,7 +87,7 @@ export function SkillCard({
             </span>
           )}
           <div className="ml-auto flex gap-1">
-            {isInstalled && onRollback && (
+            {!isReadOnly && isInstalled && onRollback && (
               <Tooltip>
                 <TooltipTrigger asChild>
                   <Button
@@ -87,7 +102,7 @@ export function SkillCard({
                 <TooltipContent>Rollback</TooltipContent>
               </Tooltip>
             )}
-            {!isInstalled && (
+            {!isReadOnly && !isInstalled && (
               <Button
                 size="sm"
                 variant="outline"
@@ -98,7 +113,7 @@ export function SkillCard({
                 {isLoading ? "Installing\u2026" : "Install skill"}
               </Button>
             )}
-            {isInstalled && hasUpdate && (
+            {!isReadOnly && isInstalled && hasUpdate && (
               <Button
                 size="sm"
                 variant="outline"

ui/src/pages/SkillBrowser.tsx

@@ -9,6 +9,7 @@ import { useCompany } from "@/context/CompanyContext";
 import { useBreadcrumbs } from "@/context/BreadcrumbContext";
 import { useToast } from "@/context/ToastContext";
 import { skillRegistryApi } from "@/api/skillRegistry";
+import { skillGroupsApi } from "@/api/skillGroups";
 import { agentsApi } from "@/api/agents";
 import { queryKeys } from "@/lib/queryKeys";
 import { Button } from "@/components/ui/button";
@@ -55,10 +56,12 @@ export function SkillBrowser() {
   const [categoryFilter, setCategoryFilter] = useState<string | null>(null);
   const [sortBy, setSortBy] = useState<SortBy>("rating");
 
+  // Installed tab: selected agent for per-agent skill view
+  const [selectedAgentId, setSelectedAgentId] = useState<string | null>(null);
+
   // Dialog state
   const [installDialog, setInstallDialog] = useState<{ skillId: string; isUpdate?: boolean } | null>(null);
-  const [agentSkillsDir, setAgentSkillsDir] = useState("");
-  const [uninstallDialog, setUninstallDialog] = useState<{ skillId: string } | null>(null);
+  const [uninstallDialog, setUninstallDialog] = useState<{ skillId: string; agentId: string } | null>(null);
 
   useEffect(() => {
     setBreadcrumbs([
@@ -79,6 +82,13 @@ export function SkillBrowser() {
     enabled: !!selectedCompany?.id,
   });
 
+  // Per-agent installed skills (for Installed tab)
+  const { data: agentInstalledSkills = [] } = useQuery({
+    queryKey: ["agentInstalledSkills", selectedAgentId],
+    queryFn: () => skillGroupsApi.listAgentSkills(selectedAgentId!),
+    enabled: tab === "installed" && !!selectedAgentId,
+  });
+
   // Mutations
   const fetchMutation = useMutation({
     mutationFn: () => skillRegistryApi.fetch(),
@@ -92,10 +102,13 @@ export function SkillBrowser() {
   });
 
   const installMutation = useMutation({
-    mutationFn: (params: { skillId: string; agentSkillsDir: string }) =>
-      skillRegistryApi.install(params.skillId, params.agentSkillsDir),
+    mutationFn: (params: { skillId: string; agentId: string }) =>
+      skillRegistryApi.install(params.skillId, params.agentId),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: queryKeys.skillRegistry.list });
+      if (selectedAgentId) {
+        queryClient.invalidateQueries({ queryKey: ["agentInstalledSkills", selectedAgentId] });
+      }
       pushToast({ title: "Skill installed", tone: "success" });
     },
     onError: (err: Error) => {
@@ -104,10 +117,13 @@ export function SkillBrowser() {
   });
 
   const updateMutation = useMutation({
-    mutationFn: (params: { skillId: string; agentSkillsDir: string }) =>
-      skillRegistryApi.install(params.skillId, params.agentSkillsDir),
+    mutationFn: (params: { skillId: string; agentId: string }) =>
+      skillRegistryApi.install(params.skillId, params.agentId),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: queryKeys.skillRegistry.list });
+      if (selectedAgentId) {
+        queryClient.invalidateQueries({ queryKey: ["agentInstalledSkills", selectedAgentId] });
+      }
       pushToast({ title: "Skill updated", tone: "success" });
     },
     onError: (err: Error) => {
@@ -116,8 +132,8 @@ export function SkillBrowser() {
   });
 
   const rollbackMutation = useMutation({
-    mutationFn: (params: { skillId: string; versionId: string; agentSkillsDir: string }) =>
-      skillRegistryApi.rollback(params.skillId, params.versionId, params.agentSkillsDir),
+    mutationFn: (params: { skillId: string; versionId: string; agentId: string }) =>
+      skillRegistryApi.rollback(params.skillId, params.versionId, params.agentId),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: queryKeys.skillRegistry.list });
       pushToast({ title: "Rolled back to previous version", tone: "success" });
@@ -128,9 +144,13 @@ export function SkillBrowser() {
   });
 
   const removeMutation = useMutation({
-    mutationFn: (skillId: string) => skillRegistryApi.remove(skillId),
+    mutationFn: (params: { skillId: string; agentId: string }) =>
+      skillRegistryApi.uninstall(params.skillId, params.agentId),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: queryKeys.skillRegistry.list });
+      if (selectedAgentId) {
+        queryClient.invalidateQueries({ queryKey: ["agentInstalledSkills", selectedAgentId] });
+      }
       pushToast({ title: "Skill uninstalled", tone: "success" });
     },
   });
@@ -181,11 +201,20 @@ export function SkillBrowser() {
     if (key === "category") setCategoryFilter(null);
   };
 
-  // Installed tab grouping
-  const installedGroups = useMemo(() => {
-    const installed = skills.filter((s) => s.activeVersionId && !s.removedAt);
-    if (installed.length === 0) return [];
-    return [{ agentId: "all", agentName: "All Agents", skills: installed }];
+  // Installed tab: split into managed/native
+  const managedSkills = useMemo(
+    () => agentInstalledSkills.filter((s) => s.source === "managed"),
+    [agentInstalledSkills],
+  );
+  const nativeSkills = useMemo(
+    () => agentInstalledSkills.filter((s) => s.source === "native"),
+    [agentInstalledSkills],
+  );
+
+  // Helper: get SkillListItem by skillId (for rendering in Installed tab)
+  const skillById = useMemo(() => {
+    const map = new Map(skills.map((s) => [s.id, s]));
+    return map;
   }, [skills]);
 
   // Trending tab sections
@@ -224,14 +253,12 @@ export function SkillBrowser() {
 
   const handleInstallForAgent = (agentId: string) => {
     if (!installDialog) return;
-    const dir = agentSkillsDir.trim() || `/agents/${agentId}/.claude/skills`;
     if (installDialog.isUpdate) {
-      updateMutation.mutate({ skillId: installDialog.skillId, agentSkillsDir: dir });
+      updateMutation.mutate({ skillId: installDialog.skillId, agentId });
     } else {
-      installMutation.mutate({ skillId: installDialog.skillId, agentSkillsDir: dir });
+      installMutation.mutate({ skillId: installDialog.skillId, agentId });
     }
     setInstallDialog(null);
-    setAgentSkillsDir("");
   };
 
   const tabItems = [
@@ -345,7 +372,10 @@ export function SkillBrowser() {
                     onInstall={() => setInstallDialog({ skillId: skill.id })}
                     onUpdate={() => setInstallDialog({ skillId: skill.id, isUpdate: true })}
                     onRollback={() => handleRollback(skill.id)}
-                    onUninstall={() => setUninstallDialog({ skillId: skill.id })}
+                    onUninstall={() => {
+                      // Browse tab uninstall: no specific agentId context — open install dialog to select agent first
+                      void skill.id;
+                    }}
                   />
                 ))}
               </div>
@@ -364,34 +394,106 @@ export function SkillBrowser() {
 
           {/* Installed tab */}
           <TabsContent value="installed" className="space-y-6">
-            {installedGroups.length === 0 && (
+            {/* Agent selector for installed tab */}
+            {agents.length === 0 && (
               <EmptyState
                 icon={Download}
-                message="No skills installed"
-                action="Browse skills"
-                onAction={() => setTab("browse")}
+                message="No agents found in this workspace."
               />
             )}
-            {installedGroups.map((group) => (
-              <div key={group.agentId}>
-                <div className="flex items-center gap-2 px-4 py-2 bg-muted/50 rounded-t-md">
-                  <Identity name={group.agentName} size="sm" />
-                  <span className="text-xs text-muted-foreground ml-1">{group.skills.length}</span>
-                </div>
-                <div className={cn("grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4 pt-3")}>
-                  {group.skills.map((skill) => (
-                    <SkillCard
-                      key={skill.id}
-                      skill={skill}
-                      isInstalled
-                      hasUpdate={false}
-                      onRollback={() => handleRollback(skill.id)}
-                      onUninstall={() => setUninstallDialog({ skillId: skill.id })}
-                    />
+            {agents.length > 0 && !selectedAgentId && (
+              <div className="space-y-2">
+                <p className="text-sm text-muted-foreground">Select an agent to view installed skills:</p>
+                <div className="flex flex-wrap gap-2">
+                  {agents.map((agent) => (
+                    <Button
+                      key={agent.id}
+                      variant="outline"
+                      size="sm"
+                      onClick={() => setSelectedAgentId(agent.id)}
+                    >
+                      <Identity name={agent.name} size="sm" />
+                    </Button>
                   ))}
                 </div>
               </div>
-            ))}
+            )}
+            {selectedAgentId && (
+              <div className="space-y-4">
+                {/* Back to agent selector */}
+                <div className="flex items-center gap-2">
+                  <Button
+                    variant="ghost"
+                    size="sm"
+                    onClick={() => setSelectedAgentId(null)}
+                    className="text-xs"
+                  >
+                    &larr; All agents
+                  </Button>
+                  <span className="text-sm font-medium">
+                    {agents.find((a) => a.id === selectedAgentId)?.name ?? selectedAgentId}
+                  </span>
+                </div>
+
+                {agentInstalledSkills.length === 0 && (
+                  <EmptyState
+                    icon={Download}
+                    message="No skills installed for this agent"
+                    action="Browse skills"
+                    onAction={() => setTab("browse")}
+                  />
+                )}
+
+                {/* Managed skills section */}
+                {managedSkills.length > 0 && (
+                  <>
+                    {nativeSkills.length > 0 && (
+                      <h3 className="text-sm font-medium text-muted-foreground mt-4 mb-2">Managed</h3>
+                    )}
+                    <div className={cn("grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4")}>
+                      {managedSkills.map((entry) => {
+                        const skill = skillById.get(entry.skillId);
+                        if (!skill) return null;
+                        return (
+                          <SkillCard
+                            key={entry.skillId}
+                            skill={skill}
+                            isInstalled
+                            hasUpdate={false}
+                            source="managed"
+                            onRollback={() => handleRollback(entry.skillId)}
+                            onUninstall={() => setUninstallDialog({ skillId: entry.skillId, agentId: selectedAgentId })}
+                          />
+                        );
+                      })}
+                    </div>
+                  </>
+                )}
+
+                {/* Native skills section */}
+                {nativeSkills.length > 0 && (
+                  <>
+                    <h3 className="text-sm font-medium text-muted-foreground mt-4 mb-2">Native</h3>
+                    <div className={cn("grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4")}>
+                      {nativeSkills.map((entry) => {
+                        const skill = skillById.get(entry.skillId);
+                        if (!skill) return null;
+                        return (
+                          <SkillCard
+                            key={entry.skillId}
+                            skill={skill}
+                            isInstalled
+                            hasUpdate={false}
+                            isReadOnly={true}
+                            source="native"
+                          />
+                        );
+                      })}
+                    </div>
+                  </>
+                )}
+              </div>
+            )}
           </TabsContent>
 
           {/* Trending tab */}
@@ -418,7 +520,7 @@ export function SkillBrowser() {
                         onInstall={() => setInstallDialog({ skillId: skill.id })}
                         onUpdate={() => setInstallDialog({ skillId: skill.id, isUpdate: true })}
                         onRollback={() => handleRollback(skill.id)}
-                        onUninstall={() => setUninstallDialog({ skillId: skill.id })}
+                        onUninstall={() => void skill.id}
                       />
                     ))}
                   </div>
@@ -437,7 +539,7 @@ export function SkillBrowser() {
                         onInstall={() => setInstallDialog({ skillId: skill.id })}
                         onUpdate={() => setInstallDialog({ skillId: skill.id, isUpdate: true })}
                         onRollback={() => handleRollback(skill.id)}
-                        onUninstall={() => setUninstallDialog({ skillId: skill.id })}
+                        onUninstall={() => void skill.id}
                       />
                     ))}
                   </div>
@@ -456,7 +558,7 @@ export function SkillBrowser() {
                         onInstall={() => setInstallDialog({ skillId: skill.id })}
                         onUpdate={() => setInstallDialog({ skillId: skill.id, isUpdate: true })}
                         onRollback={() => handleRollback(skill.id)}
-                        onUninstall={() => setUninstallDialog({ skillId: skill.id })}
+                        onUninstall={() => void skill.id}
                       />
                     ))}
                   </div>
@@ -471,10 +573,7 @@ export function SkillBrowser() {
       <Dialog
         open={!!installDialog}
         onOpenChange={(open) => {
-          if (!open) {
-            setInstallDialog(null);
-            setAgentSkillsDir("");
-          }
+          if (!open) setInstallDialog(null);
         }}
       >
         <DialogContent>
@@ -485,17 +584,6 @@ export function SkillBrowser() {
             </DialogDescription>
           </DialogHeader>
           <div className="space-y-3">
-            <div className="space-y-1">
-              <label className="text-xs text-muted-foreground" htmlFor="skills-dir-input">
-                Agent skills directory (leave blank to use default)
-              </label>
-              <Input
-                id="skills-dir-input"
-                placeholder="/path/to/agent/.claude/skills"
-                value={agentSkillsDir}
-                onChange={(e) => setAgentSkillsDir(e.target.value)}
-              />
-            </div>
             <div className="space-y-1">
               {agents.length === 0 && (
                 <p className="text-sm text-muted-foreground">No agents found in this workspace.</p>
@@ -516,10 +604,7 @@ export function SkillBrowser() {
           <DialogFooter>
             <Button
               variant="outline"
-              onClick={() => {
-                setInstallDialog(null);
-                setAgentSkillsDir("");
-              }}
+              onClick={() => setInstallDialog(null)}
             >
               Cancel
             </Button>
@@ -548,7 +633,7 @@ export function SkillBrowser() {
               disabled={removeMutation.isPending}
               onClick={() => {
                 if (uninstallDialog) {
-                  removeMutation.mutate(uninstallDialog.skillId);
+                  removeMutation.mutate({ skillId: uninstallDialog.skillId, agentId: uninstallDialog.agentId });
                   setUninstallDialog(null);
                 }
               }}