test(multiple-subtitles): [PKG-MULTI-SUB-01] freeze contracts and verify parser provenance

refactor/tasks.json

@@ -2254,11 +2254,16 @@
       "dependsOn": [
         "BASE-05"
       ],
-      "status": "todo",
+      "status": "done",
       "risk": "H",
       "deliverable": "subtitles/onParser、multipleSubtitles 名称及实际返回方法",
       "acceptance": "源码/声明/README/demo/发布包差异已登记；公开形状和版本范围冻结；接续 VENDOR-03，定位 WebVTT parser 来源/修订及 CC0 头，保留解析/序列化行为",
-      "evidence": []
+      "evidence": [
+        "baselines/multiple-subtitles-release.json",
+        "baselines/multiple-subtitles-contract.md",
+        "baselines/multiple-subtitles-contract-validation.json",
+        "changes/2026-09-13-PKG-MULTI-SUB-01-contract.md"
+      ]
     },
     {
       "id": "PKG-MULTI-SUB-02",