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

envelope_test.go

@@ -0,0 +1,52 @@
+package notify
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestBuildFileIDUniqueAcrossBurst(t *testing.T) {
+	const total = 512
+	seen := make(map[string]struct{}, total)
+	for i := 0; i < total; i++ {
+		id := buildFileID("report.txt")
+		if _, ok := seen[id]; ok {
+			t.Fatalf("duplicate file id generated: %q", id)
+		}
+		seen[id] = struct{}{}
+	}
+}
+
+func TestBuildFileIDKeepsReadableBaseName(t *testing.T) {
+	id := buildFileID("/tmp/demo/report.txt")
+	if !strings.HasPrefix(id, "report.txt-") {
+		t.Fatalf("unexpected file id prefix: %q", id)
+	}
+
+	parts := strings.Split(id, "-")
+	if got, want := len(parts), 5; got != want {
+		t.Fatalf("unexpected file id segment count: got %d want %d, id=%q", got, want, id)
+	}
+	for _, part := range parts[1:] {
+		if part == "" {
+			t.Fatalf("unexpected empty file id segment: %q", id)
+		}
+	}
+}
+
+func TestBuildFileIDFallsBackToUnnamedBase(t *testing.T) {
+	id := buildFileID("")
+	if !strings.HasPrefix(id, "unnamed-") {
+		t.Fatalf("unexpected unnamed file id prefix: %q", id)
+	}
+}
+
+func TestNewFileMetaEnvelopeKeepsOptionalMeta(t *testing.T) {
+	env := newFileMetaEnvelope("file-1", "/tmp/demo/report.txt", 123, "sum", 0o640, 123456789)
+	if got, want := env.File.Mode, uint32(0o640); got != want {
+		t.Fatalf("mode mismatch: got %o want %o", got, want)
+	}
+	if got, want := env.File.ModTime, int64(123456789); got != want {
+		t.Fatalf("modtime mismatch: got %d want %d", got, want)
+	}
+}