cdc may be stuck in logpuller PriorityQueue

PriorityQueue.Pop() will block and wait for pq.signal when called on an empty queue, but PriorityQueue.Close() only clears the heap and does not close or notify pq.signal. So if a goroutine is currently calling Pop() on an empty queue, it will not be awakened by Close(). Then this waiting party is not fake; it is a real consumer in the main chain: subscriptionClient.handleRegions() will loop and call s.regionTaskQueue.Pop(ctx). The ctx it passes in is the ctx derived from errgroup in Run(), not subscriptionClient's own s.ctx. So the key point is: although subscriptionClient.Close() will do s.cancel() and s.regionTaskQueue.Close(), if the outer Run()'s errgroup ctx hasn't been canceled yet, handleRegions() might continue to get stuck on Pop(ctx). The final manifestation is that shutdown doesn't complete cleanly, and Run() might hang.