fix: 清理AI遗留代码，修复场景配置

- 删除三套旧菜单系统 (MainMenu.cs, MainMenuUI.cs, ModeSelectionUI.cs)
- Ground 添加 BoxCollider 并设置 tag 为 Ground
- UIManager.OnReturnClicked 改为通过 PageController 返回首页
- PageController 增加 ReturnToHome 方法，管理 BtnFixationBack 可见性
- 清理废弃场景 Experiment.unity / ModeSelection.unity 及历史截图

Doc/WebGLBuildSever/node_modules/inherits/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "inherits",
+  "description": "Browser-friendly inheritance fully compatible with standard node.js inherits()",
+  "version": "2.0.4",
+  "keywords": [
+    "inheritance",
+    "class",
+    "klass",
+    "oop",
+    "object-oriented",
+    "inherits",
+    "browser",
+    "browserify"
+  ],
+  "main": "./inherits.js",
+  "browser": "./inherits_browser.js",
+  "repository": "git://github.com/isaacs/inherits",
+  "license": "ISC",
+  "scripts": {
+    "test": "tap"
+  },
+  "devDependencies": {
+    "tap": "^14.2.4"
+  },
+  "files": [
+    "inherits.js",
+    "inherits_browser.js"
+  ]
+}