test(chapter): PKG-CHAPTER-02 cover behavior and optional factory types

refactor/tasks.json

@@ -1161,11 +1161,14 @@
         "ENG-03",
         "ENG-05"
       ],
-      "status": "todo",
+      "status": "done",
       "risk": "M",
       "deliverable": "区间重叠/空列表/边界 seek、hover 标题和 update 用例",
       "acceptance": "旧版本行为可重跑，成功/失败/切源/销毁有必要断言；修正 BASE-TYPE-02 的可选参数声明并补正反例",
-      "evidence": []
+      "evidence": [
+        "changes/2026-09-10-PKG-CHAPTER-02-tests.md",
+        "baselines/chapter-validation.json"
+      ]
     },
     {
       "id": "PKG-CHAPTER-03",