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

envelope.go

@@ -2,13 +2,16 @@ package notify
 
 import (
 	"b612.me/notify/internal/timeutil"
+	"context"
 	crand "crypto/rand"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync/atomic"
+	"time"
 )
 
 type EnvelopeKind uint8
@@ -30,6 +33,11 @@ type Envelope struct {
 	Body   []byte
 	Stream StreamPacket
 	File   FilePacket
+
+	controlCtx       context.Context
+	controlPriority  controlPriority
+	controlTimeout   time.Duration
+	transportProfile *transportProtectionProfile
 }
 
 type StreamPacket struct {
@@ -56,12 +64,31 @@ func wrapTransferMsgEnvelope(msg TransferMsg, enFn func(interface{}) ([]byte, er
 		return Envelope{}, err
 	}
 	return Envelope{
-		Kind: EnvelopeSignal,
-		ID:   msg.ID,
-		Body: body,
+		Kind:            EnvelopeSignal,
+		ID:              msg.ID,
+		Body:            body,
+		controlPriority: controlPriorityForTransferMessage(msg),
 	}, nil
 }
 
+func controlPriorityForTransferMessage(msg TransferMsg) controlPriority {
+	switch msg.Type {
+	case MSG_SYS, MSG_SYS_WAIT, MSG_SYS_REPLY, MSG_KEY_CHANGE, MSG_SYNC_REPLY:
+		return controlPriorityCritical
+	}
+	if msg.Key == "heartbeat" || msg.Key == "bye" || strings.HasPrefix(msg.Key, "notify.") {
+		return controlPriorityCritical
+	}
+	return controlPriorityNormal
+}
+
+func (env Envelope) controlContext() context.Context {
+	if env.controlCtx == nil {
+		return context.Background()
+	}
+	return env.controlCtx
+}
+
 func unwrapTransferMsgEnvelope(env Envelope, deFn func([]byte) (interface{}, error)) (TransferMsg, error) {
 	if env.Kind != EnvelopeSignal {
 		return TransferMsg{}, errors.New("envelope kind is not signal")
@@ -79,8 +106,9 @@ func unwrapTransferMsgEnvelope(env Envelope, deFn func([]byte) (interface{}, err
 
 func newSignalAckEnvelope(signalID uint64) Envelope {
 	return Envelope{
-		Kind: EnvelopeSignalAck,
-		ID:   signalID,
+		Kind:            EnvelopeSignalAck,
+		ID:              signalID,
+		controlPriority: controlPriorityCritical,
 	}
 }