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

bulk_dedicated.go

@@ -221,6 +221,9 @@ func writeBulkDedicatedRecordWithDeadline(conn net.Conn, payload []byte, deadlin
 	if conn == nil {
 		return net.ErrClosed
 	}
+	if deadline.IsZero() {
+		deadline = writeDeadlineFromTimeout(defaultBulkDataWriteTimeout)
+	}
 	return withRawConnWriteLockDeadline(conn, deadline, func(conn net.Conn) error {
 		var header [bulkDedicatedRecordHeaderLen]byte
 		copy(header[:4], bulkDedicatedRecordMagic)
@@ -648,6 +651,9 @@ func (c *ClientCommon) sendDedicatedBulkAttachRequest(ctx context.Context, conn
 	if bulk == nil {
 		return bulkAttachResponse{}, errBulkIDEmpty
 	}
+	if ctx == nil {
+		ctx = context.Background()
+	}
 	defer func() {
 		_ = conn.SetReadDeadline(time.Time{})
 	}()
@@ -670,7 +676,16 @@ func (c *ClientCommon) sendDedicatedBulkAttachRequest(ctx context.Context, conn
 	if err != nil {
 		return bulkAttachResponse{}, err
 	}
-	if err := writeFullToConn(conn, frame); err != nil {
+	if err := ctx.Err(); err != nil {
+		return bulkAttachResponse{}, err
+	}
+	deadline := earlierWriteDeadline(
+		writeDeadlineFromTimeout(c.maxWriteTimeoutSnapshot()),
+		contextDeadline(ctx),
+	)
+	if err := withRawConnWriteLockDeadline(conn, deadline, func(conn net.Conn) error {
+		return writeFullToConnUnlocked(conn, frame)
+	}); err != nil {
 		return bulkAttachResponse{}, err
 	}
 	if deadline, ok := ctx.Deadline(); ok {
@@ -1019,7 +1034,11 @@ func (s *ServerCommon) replyDedicatedBulkAttachDetached(client *LogicalConn, con
 	if err != nil {
 		return err
 	}
-	return withRawConnWriteLockDeadline(conn, writeDeadlineFromTimeout(client.maxWriteTimeoutSnapshot()), func(conn net.Conn) error {
+	deadline := earlierWriteDeadline(
+		writeDeadlineFromTimeout(defaultBulkDedicatedHelloTimeout),
+		writeDeadlineFromTimeout(client.maxWriteTimeoutSnapshot()),
+	)
+	return withRawConnWriteLockDeadline(conn, deadline, func(conn net.Conn) error {
 		return writeFullToConnUnlocked(conn, frame)
 	})
 }