test: 补齐短时间可测验收并修复建群下行卡住

internal/app/group/app.go

@@ -660,6 +660,7 @@ func (a *App) emit(ctx context.Context, recipients []string, groupID, event, end
 	if a.down == nil {
 		return
 	}
+	_ = ctx
 	frame := protocol.GroupEvent{
 		V: protocol.Version, Type: protocol.TypeGroupEvent,
 		GroupID: groupID, Event: event, EndpointID: endpointID, AtMs: atMs,
@@ -668,14 +669,20 @@ func (a *App) emit(ctx context.Context, recipients []string, groupID, event, end
 	if encErr != nil {
 		return
 	}
-	seen := map[string]struct{}{}
-	for _, id := range recipients {
-		if _, ok := seen[id]; ok {
-			continue
+	// 异步且略推迟：必须让处理该端上行的 worker 先 PublishDown resp。
+	// 若与 resp 同时向本连接注入 group_event，会与 mochi InlineClient 互相等待。
+	ids := append([]string(nil), recipients...)
+	go func() {
+		time.Sleep(20 * time.Millisecond)
+		seen := map[string]struct{}{}
+		for _, id := range ids {
+			if _, ok := seen[id]; ok {
+				continue
+			}
+			seen[id] = struct{}{}
+			_ = a.down.PublishDown(context.Background(), id, "", payload, port.PublishOpts{QoS: 0})
 		}
-		seen[id] = struct{}{}
-		_ = a.down.PublishDown(ctx, id, "", payload, port.PublishOpts{QoS: 0})
-	}
+	}()
 }
 
 func encodeFrame(v any) ([]byte, error) {