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/routes/lanes.js

@@ -15,6 +15,7 @@ const path = require("node:path");
 const { db } = require("../db");
 const lanesLib = require("../lib/lanes");
 const { sessionWorktree, removeSessionWorktree } = require("../lib/session-worktree");
+const { suggestCommitMessage } = require("../lib/commit-message");
 const aiTools = require("../lib/ai-tools");
 const {
   listPipelines,
@@ -1061,6 +1062,27 @@ router.get("/:id/git/branches", async (req, res) => {
  * rule about what each action may do lives in server/lib/git-ops.js, not here.
  * `git pull` is --ff-only and `switch` refuses a dirty tree, by design there.
  */
+/**
+ * A commit message suggested by the user's `claude` CLI for what is STAGED
+ * (server/lib/commit-message.js). Not a git write — it only reads the index —
+ * but same-origin, because each call spends the user's Claude quota.
+ * Registered before `/:id/git/:action`, which would answer EBADACTION.
+ */
+router.post("/:id/git/commit-message", sameOriginGuard, async (req, res) => {
+  const t = await gitTargetOr404(req, res);
+  if (!t) return;
+  try {
+    res.json({ message: await suggestCommitMessage(t.cwd) });
+  } catch (err) {
+    const status = ["ENOSTAGED", "ENOTOOL"].includes(err.code)
+      ? 400
+      : err.code === "EAI"
+        ? 502
+        : 500;
+    res.status(status).json({ error: { code: gitErrorCode(err), message: err.message } });
+  }
+});
+
 router.post("/:id/git/:action", sameOriginGuard, async (req, res) => {
   const t = await gitTargetOr404(req, res);
   if (!t) return;