worker: heartbeat parent task during marker poll/wait loops

Marker waits run after _run_attempt has cleared _running, so the run_loop heartbeat thread no longer refreshes the waiting parent. sweep_stale_tasks (default 300s) then kills a parent waiting up to the 3600s marker timeout, as seen in the marker live test (PM2 swept mid wait-threads). Poll and wait loops now heartbeat the parent each iteration (interval clamped to <=60s, well under the 300s threshold), best-effort, without touching _running, so no new capacity leak and cancel still works (empty _running entry has no proc/container to kill). Tests: 2 new sweep-survival tests (stale heartbeat at -299s, 2s wait, sweep must spare the parent); both fail 2/2 on pre-fix code and pass with the fix.

cloud/worker.py

@@ -2402,6 +2402,15 @@ class Worker:
             if self._was_cancelled(task["id"]):
                 cancelled = True
                 break
+            # 等候中父任务自己刷心跳：标记等待在 _run_attempt 返回后
+            # 才跑，那时 _running 已被清掉，run_loop 的心跳线程刷
+            # 不到它；不自刷的话，sweep（默认 300 秒）会在父任务
+            # 等到 3600 秒上限之前把它当死任务误杀。每次循环刷一次，
+            # 间隔至多 interval（钳制后 <=60 秒），远小于 300 秒阈值。
+            try:
+                self.heartbeat(task["id"])
+            except Exception:
+                pass
             try:
                 conn = _db_connect(self.db_path)
                 try:
@@ -2450,6 +2459,12 @@ class Worker:
             if self._was_cancelled(task["id"]):
                 cancelled = True
                 break
+            # 与 _poll_task_snapshot 同款：等候中父任务自己刷心跳，
+            # 否则 sweep（默认 300 秒）会误杀最长可等 3600 秒的父任务。
+            try:
+                self.heartbeat(task["id"])
+            except Exception:
+                pass
             pending = [tid for tid in target_ids if tid not in resolved]
             if not pending:
                 break