feat(scripts): legacy-layer 转换器脚手架 + fixtures + 解码 smoke test

- 添加 iconv-lite + @xmldom/xmldom 依赖 (YouleNexus + 顶层)
- 创建 framework-tests/legacy-layer-migration/ 目录结构
- 复制 Game_Surface_3 gameabc_Image.json / Layer00002.xml / Login_Layer.prefab 作 fixtures
- spirit-semantics.json 骨架 (Task 5 完整化)
- _smoke-iconv.mjs 验证解码可读中文 Spirit 名

注意: 顶层 package.json 也加了 iconv-lite/@xmldom/xmldom
(转换工具将在 cocoscreator_projects/scripts/ 跑, smoke test 也从
cocoscreator_projects 跑; 只装 YouleNexus 无法解析 iconv-lite).
另: 实际 Layer00002.xml 是 UTF-8 (XML 头声明 + 字节验证), 不是
spec/brief 假设的 GB18030 - smoke test 用 UTF-8 解码才能读到
'微信登录背景'. 转换工具后续 Task 应支持自动检测 (XML 声明优先,
fallback GB18030).

cocoscreator_projects/YouleNexus/package-lock.json

@@ -0,0 +1,45 @@
+{
+  "name": "YouleNexus",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "YouleNexus",
+      "dependencies": {
+        "@xmldom/xmldom": "^0.9.12",
+        "iconv-lite": "^0.7.3"
+      }
+    },
+    "node_modules/@xmldom/xmldom": {
+      "version": "0.9.12",
+      "resolved": "https://registry.npmmirror.com/@xmldom/xmldom/-/xmldom-0.9.12.tgz",
+      "integrity": "sha512-5AXjrcMClTryPe9LgZrygpB1lj7s0S9E0+W+AHaVKAVyHanafK86iPSvG5xHVSp/jC+VH1UXu0TAEmY279xH7A==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=14.6"
+      }
+    },
+    "node_modules/iconv-lite": {
+      "version": "0.7.3",
+      "resolved": "https://registry.npmmirror.com/iconv-lite/-/iconv-lite-0.7.3.tgz",
+      "integrity": "sha512-IKXpvIzjnC9XTAUbVBcMfGS0EPaIXtW6v+zr+RRp+hqULEpo0owZax6wyRwPOJbWbzjYspQwusTsfVr0ifh4uQ==",
+      "license": "MIT",
+      "dependencies": {
+        "safer-buffer": ">= 2.1.2 < 3.0.0"
+      },
+      "engines": {
+        "node": ">=0.10.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/express"
+      }
+    },
+    "node_modules/safer-buffer": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmmirror.com/safer-buffer/-/safer-buffer-2.1.2.tgz",
+      "integrity": "sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==",
+      "license": "MIT"
+    }
+  }
+}