test(mediabunny): [PKG-MB-09] verify native picture-in-picture checkpoint

refactor/tasks.json

@@ -3570,11 +3570,14 @@
         "PKG-MB-08",
         "CORE-22"
       ],
-      "status": "todo",
+      "status": "doing",
       "risk": "H",
       "deliverable": "跨浏览器能力、长播放、DPiP、HLS 音轨/质量报告",
       "acceptance": "资源释放、事件顺序、AV sync 与支持范围满足基线",
-      "evidence": []
+      "evidence": [
+        "changes/2026-09-12-PKG-MB-09-native-pip-checkpoint.md",
+        "baselines/mb-native-pip-checkpoint.json"
+      ]
     },
     {
       "id": "PKG-MB-10",