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__/lanes-api.test.js

@@ -1105,6 +1105,11 @@ describe("the lane git surface: changes, branches, actions (issue #34)", () => {
     const bogus = await request("POST", `/api/lanes/${laneId}/git/rebase`, {});
     assert.equal(bogus.status, 400);
     assert.equal(bogus.body.error.code, "EBADACTION");
+
+    // Its own route, not an action: never reaches claude with nothing staged.
+    const suggest = await request("POST", `/api/lanes/${laneId}/git/commit-message`, {});
+    assert.equal(suggest.status, 400);
+    assert.equal(suggest.body.error.code, "ENOSTAGED");
   });
 
   it("400s a publish to a url that is not https, ssh or scp-like", async () => {