feat(22-02): ChatMessageIdentityBar, ChatStreamingCursor, and extended ChatMessage

- Create ChatMessageIdentityBar with agent icon, name, timestamp, and streaming dot
- Create ChatStreamingCursor with animate-cursor-blink and aria-hidden
- Extend ChatMessage with agentName, agentIcon, agentRole, timestamp, isStreaming props
- Wrap assistant messages in group div for hover actions (Plan 03)
- Create agent-role-colors.ts with 11 distinct role colors (light + dark variants)
- Create ChatMarkdownMessage prerequisite from phase-21 base
- All 4 ChatMessageIdentityBar tests pass

ui/src/components/ChatMessage.tsx

@@ -1,12 +1,28 @@
 import { ChatMarkdownMessage } from "./ChatMarkdownMessage";
+import { ChatMessageIdentityBar } from "./ChatMessageIdentityBar";
+import { ChatStreamingCursor } from "./ChatStreamingCursor";
 import { cn } from "../lib/utils";
+import type { AgentRole } from "@paperclipai/shared";
 
 interface ChatMessageProps {
   role: "user" | "assistant" | "system";
   content: string;
+  agentName?: string | null;
+  agentIcon?: string | null;
+  agentRole?: AgentRole | null;
+  timestamp?: string;
+  isStreaming?: boolean;
 }
 
-export function ChatMessage({ role, content }: ChatMessageProps) {
+export function ChatMessage({
+  role,
+  content,
+  agentName,
+  agentIcon,
+  agentRole,
+  timestamp,
+  isStreaming,
+}: ChatMessageProps) {
   if (role === "user") {
     return (
       <div className="flex justify-end">
@@ -22,8 +38,18 @@ export function ChatMessage({ role, content }: ChatMessageProps) {
   }
   // assistant or system
   return (
-    <div className="max-w-full">
+    <div className="max-w-full group relative">
+      {agentName && (
+        <ChatMessageIdentityBar
+          agentName={agentName}
+          agentIcon={agentIcon}
+          agentRole={agentRole}
+          timestamp={timestamp}
+          isStreaming={isStreaming}
+        />
+      )}
       <ChatMarkdownMessage content={content} />
+      {isStreaming && <ChatStreamingCursor />}
     </div>
   );
 }

ui/src/components/ChatMessageIdentityBar.test.tsx

@@ -1,8 +1,66 @@
-import { describe, it } from "vitest";
+// @vitest-environment jsdom
+import { act } from "react";
+import { createRoot } from "react-dom/client";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { ChatMessageIdentityBar } from "./ChatMessageIdentityBar";
+
+// Tell React this environment uses act() for event flushing.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
 
 describe("ChatMessageIdentityBar", () => {
-  it.todo("renders agent icon at 16x16px");
-  it.todo("renders agent name in semibold text");
-  it.todo("renders timestamp in muted text");
-  it.todo("applies role-specific color from agentRoleColors");
+  let container: HTMLDivElement;
+  let root: ReturnType<typeof createRoot> | null = null;
+
+  beforeEach(() => {
+    container = document.createElement("div");
+    document.body.appendChild(container);
+    root = null;
+  });
+
+  afterEach(() => {
+    if (root) {
+      act(() => {
+        root!.unmount();
+      });
+      root = null;
+    }
+    if (container.parentNode) {
+      container.remove();
+    }
+  });
+
+  function render(props: Parameters<typeof ChatMessageIdentityBar>[0]) {
+    root = createRoot(container);
+    act(() => {
+      root!.render(<ChatMessageIdentityBar {...props} />);
+    });
+    return container;
+  }
+
+  it("renders agent name in semibold text", () => {
+    render({ agentName: "PM Agent" });
+    const nameEl = container.querySelector(".font-semibold");
+    expect(nameEl).toBeDefined();
+    expect(nameEl?.textContent).toBe("PM Agent");
+  });
+
+  it("renders timestamp when provided", () => {
+    render({ agentName: "Test", timestamp: "2026-01-01T12:30:00Z" });
+    const allText = container.textContent ?? "";
+    expect(allText).toContain("12:30");
+  });
+
+  it("applies role-specific color class", () => {
+    render({ agentName: "PM", agentRole: "pm" });
+    const nameEl = container.querySelector(".font-semibold");
+    expect(nameEl?.className).toContain("text-blue-600");
+    expect(nameEl?.className).toContain("dark:text-blue-400");
+  });
+
+  it("shows streaming indicator dot when isStreaming", () => {
+    render({ agentName: "Test", isStreaming: true });
+    const dot = container.querySelector(".animate-pulse");
+    expect(dot).not.toBeNull();
+  });
 });

ui/src/components/ChatMessageIdentityBar.tsx

@@ -0,0 +1,38 @@
+import { AgentIcon } from "./AgentIconPicker";
+import { agentRoleColors, agentRoleColorDefault } from "../lib/agent-role-colors";
+import type { AgentRole } from "@paperclipai/shared";
+
+interface ChatMessageIdentityBarProps {
+  agentName: string;
+  agentIcon?: string | null;
+  agentRole?: AgentRole | null;
+  timestamp?: string;
+  isStreaming?: boolean;
+}
+
+export function ChatMessageIdentityBar({
+  agentName,
+  agentIcon,
+  agentRole,
+  timestamp,
+  isStreaming,
+}: ChatMessageIdentityBarProps) {
+  const colorClass = agentRole
+    ? (agentRoleColors[agentRole] ?? agentRoleColorDefault)
+    : agentRoleColorDefault;
+
+  return (
+    <div className="flex items-center gap-2 mb-1">
+      <AgentIcon icon={agentIcon} className={`h-4 w-4 ${colorClass}`} />
+      <span className={`text-[13px] font-semibold ${colorClass}`}>{agentName}</span>
+      {isStreaming && (
+        <span className="h-1.5 w-1.5 rounded-full bg-cyan-400 animate-pulse" />
+      )}
+      {timestamp && (
+        <span className="text-[11px] text-muted-foreground">
+          {new Date(timestamp).toLocaleTimeString([], { hour: "2-digit", minute: "2-digit" })}
+        </span>
+      )}
+    </div>
+  );
+}

ui/src/components/ChatStreamingCursor.tsx

@@ -0,0 +1,8 @@
+export function ChatStreamingCursor() {
+  return (
+    <span
+      className="inline-block w-2 h-[1em] bg-foreground/70 animate-cursor-blink ml-0.5 align-text-bottom"
+      aria-hidden="true"
+    />
+  );
+}