fix(worker): make cancellation teardown failure-safe

apps/agent-worker/src/heartbeat-controller.ts

@@ -0,0 +1,42 @@
+export const createHeartbeatController = (args: {
+  intervalMs: number;
+  heartbeat: (jobId: string) => Promise<{ cancelRequested: boolean }>;
+  onCancel: (jobId: string) => Promise<void>;
+  onError: (error: unknown) => void;
+}) => {
+  const timers = new Map<string, ReturnType<typeof setInterval>>();
+  const inFlight = new Set<string>();
+
+  const stop = (jobId: string) => {
+    const timer = timers.get(jobId);
+    if (timer) clearInterval(timer);
+    timers.delete(jobId);
+  };
+
+  const tick = async (jobId: string) => {
+    if (inFlight.has(jobId) || !timers.has(jobId)) return;
+    inFlight.add(jobId);
+    try {
+      const result = await args.heartbeat(jobId);
+      if (result.cancelRequested) {
+        stop(jobId);
+        await args.onCancel(jobId);
+      }
+    } catch (error) {
+      args.onError(error);
+    } finally {
+      inFlight.delete(jobId);
+    }
+  };
+
+  return {
+    start: (jobId: string) => {
+      stop(jobId);
+      const timer = setInterval(() => void tick(jobId), args.intervalMs);
+      timer.unref();
+      timers.set(jobId, timer);
+    },
+    stop,
+    has: (jobId: string) => timers.has(jobId),
+  };
+};