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/run.js

@@ -158,6 +158,23 @@ router.get("/history", (req, res) => {
   });
 });
 
+/**
+ * Forget one closed Terminal tab (`tool = 'shell'`) from the history — the
+ * sidebar's remove. A live pane is refused; another tool's row is a 404.
+ */
+router.delete("/history/:id", (req, res) => {
+  if (runs.listRuns().some((h) => h.id === req.params.id)) {
+    return res.status(409).json({ error: { code: "ERUNLIVE", message: "terminal is still open" } });
+  }
+  const dr = require("../lib/dashboard-runs");
+  if (!dr.forgetShellRun(req.params.id)) {
+    return res
+      .status(404)
+      .json({ error: { code: "ENOTFOUND", message: "no closed terminal with that id" } });
+  }
+  res.json({ removed: req.params.id });
+});
+
 /**
  * Suggest plausible working directories. Pulls from:
  *   - "dashboard": the dashboard server's cwd