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__/router-apply.test.js

@@ -119,6 +119,33 @@ describe("routerForSpawn — Claude", () => {
   it("adds nothing for native", () => {
     assert.deepEqual(spawnFor("claude", "native"), { argv: [], env: {} });
   });
+
+  it("writes no modelPicker without behavesAs, so the user's own one still applies", () => {
+    const { name } = saveNineRouter();
+    spawnFor("claude", name);
+    const written = JSON.parse(fs.readFileSync(settingsFile(name), "utf8"));
+    assert.equal("modelPicker" in written, false);
+  });
+
+  it("maps every distinct router model name with behavesAs (issue #56)", () => {
+    const { name } = routers.createRouter({
+      label: "9Router combo",
+      baseUrl: "http://localhost:20128/v1",
+      model: "agent",
+      models: { haiku: "agent-fast", subagent: "claude-haiku-4-5-20251001" },
+      behavesAs: "claude-opus-5-5",
+    });
+    spawnFor("claude", name);
+    const written = JSON.parse(fs.readFileSync(settingsFile(name), "utf8"));
+    // A bare claude-* id is one Claude Code knows; mapping it would override
+    // its real handling.
+    assert.deepEqual(written.modelPicker, {
+      options: [
+        { model: "agent", behavesAs: "claude-opus-5-5" },
+        { model: "agent-fast", behavesAs: "claude-opus-5-5" },
+      ],
+    });
+  });
 });
 
 describe("routerForSpawn — Codex", () => {