refactor(mediabunny): [PKG-MB-08] checkpoint typed entry and compatible media declarations

refactor/tasks.json

@@ -3546,11 +3546,15 @@
         "ENG-04",
         "ENG-06"
       ],
-      "status": "todo",
+      "status": "doing",
       "risk": "H",
       "deliverable": "8 个自有 JS 模块迁移与 Result/shim 类型",
       "acceptance": "解码器/Stream/DOM 类型清楚，旧 Option 和 art.mediabunny 使用保持",
-      "evidence": []
+      "evidence": [
+        "baselines/mb-entry-source.json",
+        "changes/2026-09-12-PKG-MB-08-entry-checkpoint.md",
+        "baselines/mb-entry-checkpoint.json"
+      ]
     },
     {
       "id": "PKG-MB-09",