perf: batch group unread fanout

server/store/group_message_runtime.go

@@ -392,6 +392,13 @@ func StartRealtimeFanoutSubscriber(ctx context.Context, nodeID string, handler f
 	return groupMsgRuntime.StartRealtimeFanoutSubscriber(ctx, nodeID, handler)
 }
 
+// RealtimeFanoutEnabled reports whether Redis Pub/Sub fanout is configured.
+// Callers use it to retain the native routing fallback when Redis is disabled.
+func RealtimeFanoutEnabled() bool {
+	runtime, ok := groupMsgRuntime.(*redisGroupMessageRuntime)
+	return ok && runtime != nil && runtime.cfg.GroupFanout
+}
+
 func CacheObject(tenantID types.TenantID, namespace, id string, value any) error {
 	if groupMsgRuntime == nil || !tenantID.IsValid() || namespace == "" || id == "" || value == nil {
 		return nil