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/lib/api.ts

@@ -2186,6 +2186,9 @@ export const api = {
       if (opts.limit) qs.set("limit", String(opts.limit));
       return request<{ items: RunHistoryItem[] }>(`/run/history?${qs.toString()}`);
     },
+    /** DELETE /api/run/history/:id - forget a closed Terminal tab (shell rows only). */
+    forgetHistory: (id: string) =>
+      request<{ removed: string }>(`/run/history/${encodeURIComponent(id)}`, { method: "DELETE" }),
     /** GET /api/run/binary - whether the lane tool's CLI was found on PATH (fresh look). */
     binary: (tool: LaneTool = "claude") =>
       request<{ found: boolean; path: string | null }>(`/run/binary?tool=${tool}`),
@@ -2757,6 +2760,12 @@ export const api = {
         current: string | null;
         worktrees: LaneWorktree[];
       }>(gitUrl(id, "/branches")),
+    /**
+     * POST /api/lanes/:id/git/commit-message — a message for what is staged,
+     * written by the user's `claude` CLI (no tools, nothing persisted).
+     */
+    suggestCommitMessage: (id: GitTarget) =>
+      request<{ message: string }>(gitUrl(id, "/commit-message"), { method: "POST" }),
     /**
      * POST /api/lanes/:id/git/:action — one git write on the lane's worktree.
      * @param id The lane id.
@@ -3286,6 +3295,8 @@ export interface AiRouter {
   hasKey: boolean;
   model: string;
   models: AiRouterModels;
+  /** Claude model id the router's own model names behave as; "" when unset. */
+  behavesAs?: string;
   savedAt?: string;
 }
 
@@ -3318,6 +3329,8 @@ export interface AiRouterInput {
   model: string;
   /** Any tier left out is filled from `model`. */
   models?: Partial<AiRouterModels>;
+  /** A Claude model id; "" clears it. Omit on update to keep the stored one. */
+  behavesAs?: string;
 }
 
 /** One markdown-based config artifact (skill/agent/command/output-style),