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

server/__tests__/ai-routers.test.js

@@ -164,6 +164,21 @@ describe("ai-routers — update", () => {
   it("reports a name that does not exist", () => {
     assert.throws(() => routers.updateRouter("ghost", { label: "x" }), { code: "ENOTFOUND" });
   });
+
+  it("sets, keeps and clears behavesAs, and refuses an id that is not a Claude model's", () => {
+    const created = routers.createRouter(nineRouter({ behavesAs: " claude-opus-5-5 " }));
+    assert.equal(created.behavesAs, "claude-opus-5-5");
+    assert.equal(
+      routers.updateRouter(created.name, { label: "renamed" }).behavesAs,
+      "claude-opus-5-5"
+    );
+    assert.equal(routers.updateRouter(created.name, { behavesAs: "" }).behavesAs, "");
+    for (const bad of ["agent", "claude opus", "-claude-x", 5]) {
+      assert.throws(() => routers.updateRouter(created.name, { behavesAs: bad }), {
+        code: "EBADMODEL",
+      });
+    }
+  });
 });
 
 describe("ai-routers — remove", () => {