test(22-00): add Wave 0 test stubs for Phase 22 components and hooks

- useStreamingChat.test.ts (5 todos)
- ChatAgentSelector.test.tsx (5 todos)
- ChatMessage.test.tsx (8 todos)
- ChatSlashCommandPopover.test.tsx (5 todos)
- ChatMentionPopover.test.tsx (4 todos)
- ChatMessageIdentityBar.test.tsx (4 todos)
- ChatMessageList.test.tsx (5 todos)

ui/src/components/ChatAgentSelector.test.tsx

@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatAgentSelector", () => {
+  it.todo("renders active agent icon and name when agentId is set");
+  it.todo("renders 'Select agent' placeholder when no agent selected");
+  it.todo("lists all workspace agents in dropdown");
+  it.todo("calls onAgentChange with new agentId on selection");
+  it.todo("shows 'No agents configured' when agent list is empty");
+});

ui/src/components/ChatMentionPopover.test.tsx

@@ -0,0 +1,8 @@
+import { describe, it } from "vitest";
+
+describe("ChatMentionPopover", () => {
+  it.todo("renders agent list filtered by query string");
+  it.todo("shows agent icon, name, and role for each item");
+  it.todo("calls onSelect with @agentName on item click");
+  it.todo("shows 'No agents found' when filter matches nothing");
+});

ui/src/components/ChatMessage.test.tsx

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+import { describe, it } from "vitest";
+
+describe("ChatMessage", () => {
+  it.todo("renders user message as right-aligned bubble with plain text");
+  it.todo("renders assistant message with ChatMarkdownMessage");
+  it.todo("renders ChatMessageIdentityBar for assistant messages when agentName is provided");
+  it.todo("shows edit pencil on hover for user messages");
+  it.todo("shows retry button on hover for assistant messages");
+  it.todo("hides retry button when isStreaming is true");
+  it.todo("switches to inline edit textarea on pencil click");
+  it.todo("renders ChatStreamingCursor when isStreaming is true");
+});

ui/src/components/ChatMessageIdentityBar.test.tsx

@@ -0,0 +1,8 @@
+import { describe, it } from "vitest";
+
+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");
+});

ui/src/components/ChatMessageList.test.tsx

@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatMessageList", () => {
+  it.todo("renders messages using virtualizer");
+  it.todo("auto-scrolls to bottom when new messages arrive");
+  it.todo("shows loading skeleton when isLoading");
+  it.todo("shows empty state when no messages");
+  it.todo("appends streaming message as synthetic entry");
+});

ui/src/components/ChatSlashCommandPopover.test.tsx

@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("ChatSlashCommandPopover", () => {
+  it.todo("renders 5 slash command items when open");
+  it.todo("filters commands by typed query");
+  it.todo("calls onSelect with command string on item click");
+  it.todo("closes on Escape key");
+  it.todo("shows /search as greyed out with 'Coming soon' suffix");
+});

ui/src/hooks/useStreamingChat.test.ts

@@ -0,0 +1,9 @@
+import { describe, it } from "vitest";
+
+describe("useStreamingChat", () => {
+  it.todo("accumulates tokens from SSE data events into streamingContent");
+  it.todo("sets isStreaming=true when stream starts, false when done");
+  it.todo("clears streamingContent and invalidates query cache on done event");
+  it.todo("stop() closes the EventSource and sets isStreaming=false");
+  it.todo("handles SSE error event by closing connection");
+});