feat(notify): 重构通信内核并补齐 stream/bulk/record/transfer 能力

- 引入 LogicalConn/TransportConn 分层，ClientConn 保留兼容适配层
  - 新增 Stream、Bulk、RecordStream 三条数据面能力及对应控制路径
  - 完成 transfer/file 传输内核与状态快照、诊断能力
  - 补齐 reconnect、inbound dispatcher、modern psk 等基础模块
  - 增加大规模回归、并发与基准测试覆盖
  - 更新依赖库

signal_reliable_test.go

@@ -0,0 +1,57 @@
+package notify
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestRetryReliableSignalSendRetriesUntilAck(t *testing.T) {
+	cfg := signalReliabilityConfig{
+		AckTimeout:        10 * time.Millisecond,
+		SendRetry:         3,
+		ReceiveCacheLimit: 4,
+	}
+	pool := newSignalAckPool()
+	attempts := 0
+
+	err := retryReliableSignalSend(cfg, func(cfg signalReliabilityConfig) error {
+		attempts++
+		return sendSignalWithAck("client", 2001, cfg.AckTimeout, pool, func() error {
+			if attempts == 2 {
+				go func() {
+					time.Sleep(time.Millisecond)
+					pool.deliver("client", 2001)
+				}()
+			}
+			return nil
+		})
+	})
+	if err != nil {
+		t.Fatalf("retryReliableSignalSend should succeed after ack: %v", err)
+	}
+	if got, want := attempts, 2; got != want {
+		t.Fatalf("retry attempts mismatch: got %d want %d", got, want)
+	}
+}
+
+func TestRetryReliableSignalSendReturnsLastError(t *testing.T) {
+	wantErr := errors.New("send failed")
+	cfg := signalReliabilityConfig{
+		AckTimeout:        5 * time.Millisecond,
+		SendRetry:         2,
+		ReceiveCacheLimit: 4,
+	}
+	attempts := 0
+
+	err := retryReliableSignalSend(cfg, func(cfg signalReliabilityConfig) error {
+		attempts++
+		return wantErr
+	})
+	if !errors.Is(err, wantErr) {
+		t.Fatalf("retryReliableSignalSend should return last error: %v", err)
+	}
+	if got, want := attempts, 2; got != want {
+		t.Fatalf("retry attempts mismatch: got %d want %d", got, want)
+	}
+}