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/components/store.tsx

@@ -17,6 +17,7 @@ import {
   AuthError,
   createClient,
   type Agent,
+  type AgentEvent,
   type ApiError,
   type Approval,
   type Checkmark,
@@ -83,6 +84,9 @@ interface StoreValue {
   log: LogEntry[];
   logOffset: number;
   pageLog: (dir: 1 | -1) => void;
+  /* Headless run event stream for the selected run, oldest-first, appended by cursor
+   * polls (empty for legacy tmux agents). */
+  events: AgentEvent[];
 
   approvals: Approval[];
   hosts: Host[];
@@ -204,6 +208,9 @@ export function DashboardProvider({
   const [checkmarkMissing, setCheckmarkMissing] = useState(false);
   const [log, setLog] = useState<LogEntry[]>([]);
   const [logOffset, setLogOffset] = useState(0);
+  const [events, setEvents] = useState<AgentEvent[]>([]);
+  const eventsRef = useRef<AgentEvent[]>([]);
+  eventsRef.current = events;
   const [approvals, setApprovals] = useState<Approval[]>([]);
   const [hosts, setHosts] = useState<Host[]>([]);
   const [commands, setCommands] = useState<Command[]>([]);
@@ -282,6 +289,17 @@ export function DashboardProvider({
     } catch (e) {
       swallow(e);
     }
+    try {
+      // Cursor poll: only events newer than what we already hold come back.
+      const cur = eventsRef.current;
+      const after = cur.length ? cur[cur.length - 1].id : 0;
+      const fresh = await clientRef.current.api<AgentEvent[]>(
+        `${path}/events?after_id=${after}&limit=500`,
+      );
+      if (fresh.length) setEvents((prev) => [...prev, ...fresh]);
+    } catch (e) {
+      swallow(e);
+    }
   }, []);
 
   const loadApprovals = useCallback(async (projectId: string) => {
@@ -407,6 +425,8 @@ export function DashboardProvider({
       setCheckmark(null);
       setCheckmarkMissing(false);
       setLog([]);
+      setEvents([]);
+      eventsRef.current = [];
       void loadRun(projectId, name);
     },
     [loadRun],
@@ -925,6 +945,7 @@ export function DashboardProvider({
     log,
     logOffset,
     pageLog,
+    events,
     approvals,
     hosts,
     commands,