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__/lane-sources.test.js

@@ -185,7 +185,8 @@ describe("lane-sources instructions and launch", () => {
     let argv = null;
     tmux.__setExecImpl((args) => {
       if (args[0] === "has-session") throw Object.assign(new Error("gone"), { status: 1 });
-      if (args[0] === "new-session") argv = args.slice(args.indexOf("--") + 1);
+      // The CLI rides behind `sh -c <wait for a client> sh` (pty-run.js).
+      if (args[0] === "new-session") argv = args.slice(args.indexOf("--") + 5);
       return "";
     });
     pty.spawnRun({ laneId: lane.id, cwd: ws, initialPrompt: "-c fix it" });