refactor(mediabunny): [PKG-MB-05] own video iterators, frame pools and rendering

refactor/tasks.json

@@ -3482,11 +3482,15 @@
       "dependsOn": [
         "PKG-MB-04"
       ],
-      "status": "todo",
+      "status": "done",
       "risk": "H",
       "deliverable": "VideoEngine 调度、队列、晚帧处理和资源释放",
       "acceptance": "暂停/seek/切源无旧帧覆盖，默认丢帧策略不变",
-      "evidence": []
+      "evidence": [
+        "baselines/mb-video-source.json",
+        "changes/2026-09-12-PKG-MB-05-video.md",
+        "baselines/mb-video-validation.json"
+      ]
     },
     {
       "id": "PKG-MB-06",