feat: AI commit messages, change tree, router behavesAs, sidebar times (v2.2.0)

- Changes panel: Files and Changes merged into one panel; the overview's
  groups drawn as a folder tree (compacted chains, file counts, fold,
  stage/unstage a whole folder)
- AI-suggested commit message for what is staged
  (POST /api/lanes/:id/git/commit-message, claude -p --safe-mode, haiku)
- AI Router: optional "Behaves as" Claude model id, written as
  modelPicker options into the router's --settings file (issue #56)
- Sidebar: session rows show last activity, live rows their start time;
  a closed Terminal row can be removed (DELETE /api/run/history/:id)
- Every pane's CLI starts only once a client is attached; claude panes
  no longer forced inline; tmux scrollbar one column wide
- Update notifier: "Check for updates" reopens a closed notice

client/src/pages/__tests__/AiRouterConfig.test.tsx

@@ -104,11 +104,30 @@ describe("AiRouterConfig", () => {
         // Every tier equals the headline model, so none is sent: the server
         // fills them, which is what makes one field enough.
         models: {},
+        behavesAs: "",
         apiKey: "sk-typed",
       })
     );
   });
 
+  it("sends the typed behavesAs, which maps the router's model names in Claude Code (#56)", async () => {
+    render(<AiRouterConfig />);
+    const user = userEvent.setup();
+
+    await user.click(await screen.findByRole("button", { name: /aiRouter\.add/ }));
+    await user.type(screen.getByLabelText("aiRouter.fieldLabel"), "9Router");
+    await user.type(screen.getByLabelText("aiRouter.fieldBaseUrl"), "http://localhost:20128/v1");
+    await user.type(screen.getByLabelText("aiRouter.fieldModel"), "agent");
+    await user.type(screen.getByLabelText("aiRouter.fieldBehavesAs"), "claude-opus-5-5");
+    await user.click(screen.getByRole("button", { name: "aiRouter.save" }));
+
+    await waitFor(() =>
+      expect(api.aiRouters.create).toHaveBeenCalledWith(
+        expect.objectContaining({ model: "agent", behavesAs: "claude-opus-5-5" })
+      )
+    );
+  });
+
   it("sends only the tiers that differ from the headline model", async () => {
     render(<AiRouterConfig />);
     const user = userEvent.setup();

client/src/pages/__tests__/__snapshots__/screens.snapshot.test.tsx.snap

@@ -6981,7 +6981,7 @@ exports[`screen snapshots > Settings — about 1`] = `
             <p
               class="text-[10px] text-status-warning/90 mt-1"
             >
-              UI build v2.1.0 (rebuild client to match)
+              UI build v2.2.0 (rebuild client to match)
             </p>
           </div>
           <div