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/components/UpdateNotifier.tsx

@@ -29,8 +29,9 @@
  * ## Dismissal persistence
  * Dismissals are keyed in `localStorage` by the release tag when there is one,
  * else the upstream `remote_sha`, so a newer release re-opens the prompt while
- * a dismissed one stays dismissed. Settings can reset dismissal via the
- * `dashboard:reset-update-dismissal` window event.
+ * a dismissed one stays dismissed. The connection modal's "Check for updates"
+ * fires `dashboard:reset-update-dismissal`, which clears both the skip and the
+ * page-load close; `z-[110]` keeps this modal above that `z-[100]` one.
  *
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
@@ -184,7 +185,11 @@ export function UpdateNotifier() {
   }, [syncFromPayload]);
 
   useEffect(() => {
-    const handler = () => setDismissedSha(null);
+    // An explicit "Check for updates" undoes both kinds of close.
+    const handler = () => {
+      setDismissedSha(null);
+      setClosedKey(null);
+    };
     window.addEventListener("dashboard:reset-update-dismissal", handler);
     return () => window.removeEventListener("dashboard:reset-update-dismissal", handler);
   }, []);
@@ -313,7 +318,7 @@ export function UpdateNotifier() {
 
   return (
     <div
-      className="fixed inset-0 z-[100] flex items-center justify-center p-4 bg-surface-0/70 backdrop-blur-sm animate-fade-in"
+      className="fixed inset-0 z-[110] flex items-center justify-center p-4 bg-surface-0/70 backdrop-blur-sm animate-fade-in"
       role="dialog"
       aria-modal="true"
       aria-labelledby="update-notifier-title"