feat(control,api,ui): worker liveness + run event stream (phase 3)

- worker: heartbeat every loop pass (workers registry); reaper pass
  every ~15s marks a silent worker's running runs crashed and flips
  agents stuck in 'working' to crashed (paused/blocked keep their
  still-accurate status). Idempotent via finish_run's running-guard;
  any surviving worker can reap; no auto-requeue (half-done runs may
  have pushed). Dead workers' registry rows are dropped once settled.
- api: GET /projects/{p}/agents/{name}/events - the persisted
  stream-json event log, oldest-first, cursor-paged by row id;
  AgentOut exposes session_id/worker_id
- frontend: Run events panel in the run detail (assistant text, tool
  chips, result footer with cost/turns, runner notices, raw lines),
  cursor-appended on the existing 5s poll; 'Crashed' filter + danger
  badge; crashed agents show their frozen last frame ('last output
  before crash'); static export regenerated

Suite 290 -> 296 green; next build clean.

frontend/lib/api.ts

@@ -30,10 +30,28 @@ export interface Agent {
   working_dir: string;
   status: string;
   role?: string | null;
-  /* Latest tmux pane-tail snapshot from the worker, so the UI can show what a running
-   * agent is actually doing (and expose one wedged on an interactive prompt). */
+  /* Latest output snapshot from the worker: the tmux pane tail for legacy agents, the
+   * latest assistant text for headless runs. For a crashed agent this is the evidence
+   * frame — the last thing the process said. */
   last_output?: string | null;
   output_at?: string | null;
+  /* Headless runner: claude session UUID (null = legacy tmux agent) + supervising worker. */
+  session_id?: string | null;
+  worker_id?: string | null;
+  created_at: string;
+}
+
+/* One persisted stream-json event of a headless run (GET .../events, cursor-paged by id).
+ * `type` mirrors the stream (system/assistant/user/result) plus `worker` (runner notices)
+ * and `raw` (unparseable line kept verbatim). */
+export interface AgentEvent {
+  id: number;
+  agent_id: number;
+  run_id: number;
+  session_id?: string | null;
+  seq: number;
+  type: string;
+  payload?: Record<string, unknown> | null;
   created_at: string;
 }
 

frontend/lib/format.ts

@@ -21,6 +21,7 @@ export function statusTone(status: string | null | undefined): Tone {
     case "blocked":
     case "rejected":
     case "error":
+    case "crashed":
       return "danger";
     case "pending":
     case "queued":