feat(channels): IM 车道生成并写入真实 turn_id（user/assistant 成对 + 同源 WithTurnID；群聊隔离与静默语义不变）

internal/services/channelbridge/channelbridge_test.go

@@ -62,13 +62,15 @@ func (f *fakeAdapter) ListChannels(context.Context) ([]adapter.ChannelInfo, erro
 type stubChatter struct {
 	sessionID string
 	messages  []model.Message
+	runCtx    context.Context
 	res       *loop.Result
 	err       error
 }
 
-func (s *stubChatter) Run(_ context.Context, sessionID string, msgs []model.Message) (*loop.Result, error) {
+func (s *stubChatter) Run(ctx context.Context, sessionID string, msgs []model.Message) (*loop.Result, error) {
 	s.sessionID = sessionID
 	s.messages = msgs
+	s.runCtx = ctx
 	return s.res, s.err
 }