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

peer_error_test.go

@@ -0,0 +1,37 @@
+package notify
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"testing"
+)
+
+func TestIsTransportDetachedErrorRecognizesWrappedDetach(t *testing.T) {
+	base := transportDetachedError("dedicated bulk read error", io.ErrUnexpectedEOF)
+	for name, err := range map[string]error{
+		"direct":         base,
+		"wrapped":        fmt.Errorf("bulk reset: %w", base),
+		"transport-send": newTransportSendError(TransportSendStageTransport, base),
+	} {
+		t.Run(name, func(t *testing.T) {
+			if !IsTransportDetachedError(err) {
+				t.Fatalf("IsTransportDetachedError(%v) = false", err)
+			}
+		})
+	}
+}
+
+func TestIsTransportDetachedErrorRejectsOtherErrors(t *testing.T) {
+	for name, err := range map[string]error{
+		"nil":      nil,
+		"business": errors.New("remote file became a directory"),
+		"eof":      io.EOF,
+	} {
+		t.Run(name, func(t *testing.T) {
+			if IsTransportDetachedError(err) {
+				t.Fatalf("IsTransportDetachedError(%v) = true", err)
+			}
+		})
+	}
+}