fix(notify): 根治低带宽控制面阻塞与传输写入卡死

- 为控制消息增加优先级、公平调度、队列字节预算和自适应批处理
- 支持可取消的写门等待，收紧 shared/dedicated bulk、stream 和 Reply 写入边界
- 修复 bulk reset/close、连接 handoff 和安全 profile 切换时序
- 保留旧取消与超时错误契约，新增阶段化 TransportSendError
- 增加 ReplyCtx、ReplyObjCtx、写超时配置及黑洞连接和竞态回归测试

stream_batch_sender.go

@@ -332,18 +332,37 @@ func (s *streamBatchSender) flush(requests []streamBatchRequest) error {
 		return err
 	}
 	writeTimeout := s.transportWriteTimeout()
+	requestDeadline := streamBatchRequestsEarliestDeadline(requests)
+	writeCtx := context.Background()
+	cancelWriteCtx := func() {}
+	if !requestDeadline.IsZero() {
+		writeCtx, cancelWriteCtx = context.WithDeadline(writeCtx, requestDeadline)
+	}
+	defer cancelWriteCtx()
 	payloadBytes := 0
 	for _, payload := range payloads {
 		payloadBytes += len(payload)
 	}
 	started := time.Now()
-	err = s.binding.withConnWriteLockDeadline(writeDeadlineFromTimeout(writeTimeout), func(conn net.Conn) error {
+	lockAcquired, err := s.binding.withConnWriteLockContextStopDeadlineManaged(writeCtx, s.stopCh, writeDeadlineFromTimeout(writeTimeout), func(conn net.Conn) error {
 		return writeFramedPayloadBatchUnlocked(conn, queue, payloads)
 	})
 	s.binding.observeStreamAdaptivePayloadWrite(payloadBytes, time.Since(started), writeTimeout, err)
+	if lockAcquired && err != nil {
+		// A failed framed write may have emitted only part of a frame.
+		s.binding.closeConn()
+	}
 	return err
 }
 
+func streamBatchRequestsEarliestDeadline(requests []streamBatchRequest) time.Time {
+	var deadline time.Time
+	for _, req := range requests {
+		deadline = earlierWriteDeadline(deadline, req.deadline)
+	}
+	return deadline
+}
+
 func (s *streamBatchSender) transportWriteTimeout() time.Duration {
 	if s == nil || s.writeTimeoutProvider == nil {
 		return 0
@@ -508,6 +527,10 @@ func (s *streamBatchSender) stop() {
 		close(s.stopCh)
 	})
 	<-s.doneCh
+	// Direct submissions flush on the caller goroutine rather than run(). Wait
+	// for that path too before declaring the binding safe to hand off.
+	s.flushMu.Lock()
+	s.flushMu.Unlock()
 }
 
 func (s *streamBatchSender) failPending(err error) {