feat: 优化 DrawCurrentController 和 LotteryHallRealtimeBroadcaster 的响应结构

app/Services/Draw/LotteryHallRealtimeBroadcaster.php

@@ -21,17 +21,16 @@ final class LotteryHallRealtimeBroadcaster
         private readonly DrawHallSnapshotBuilder $snapshot,
     ) {}
 
-    /** 每秒调度：`draw.countdown` */
+    /** 每秒调度：`draw.countdown` 仅发送轻量心跳，不重查全量大厅快照。 */
     public function countdownPulse(): void
     {
         if (! $this->driverSupportsRealtime()) {
             return;
         }
 
-        $data = $this->snapshot->build();
         $ms = (int) floor(microtime(true) * 1000);
 
-        broadcast(new DrawCountdownBroadcast($data, $ms));
+        broadcast(new DrawCountdownBroadcast(null, $ms));
     }
 
     /**