docs(chapter): PKG-CHAPTER-01 freeze published behavior contracts

refactor/tasks.json

@@ -1140,11 +1140,14 @@
       "dependsOn": [
         "BASE-05"
       ],
-      "status": "todo",
+      "status": "done",
       "risk": "M",
       "deliverable": "chapters 时间区间、update、name 和进度 DOM 清单",
       "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",
-      "evidence": []
+      "evidence": [
+        "changes/2026-09-10-PKG-CHAPTER-01-contract.md",
+        "baselines/chapter-contract.md"
+      ]
     },
     {
       "id": "PKG-CHAPTER-02",