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/unpipe/README.md

@@ -0,0 +1,43 @@
+# unpipe
+
+[![NPM Version][npm-image]][npm-url]
+[![NPM Downloads][downloads-image]][downloads-url]
+[![Node.js Version][node-image]][node-url]
+[![Build Status][travis-image]][travis-url]
+[![Test Coverage][coveralls-image]][coveralls-url]
+
+Unpipe a stream from all destinations.
+
+## Installation
+
+```sh
+$ npm install unpipe
+```
+
+## API
+
+```js
+var unpipe = require('unpipe')
+```
+
+### unpipe(stream)
+
+Unpipes all destinations from a given stream. With stream 2+, this is
+equivalent to `stream.unpipe()`. When used with streams 1 style streams
+(typically Node.js 0.8 and below), this module attempts to undo the
+actions done in `stream.pipe(dest)`.
+
+## License
+
+[MIT](LICENSE)
+
+[npm-image]: https://img.shields.io/npm/v/unpipe.svg
+[npm-url]: https://npmjs.org/package/unpipe
+[node-image]: https://img.shields.io/node/v/unpipe.svg
+[node-url]: http://nodejs.org/download/
+[travis-image]: https://img.shields.io/travis/stream-utils/unpipe.svg
+[travis-url]: https://travis-ci.org/stream-utils/unpipe
+[coveralls-image]: https://img.shields.io/coveralls/stream-utils/unpipe.svg
+[coveralls-url]: https://coveralls.io/r/stream-utils/unpipe?branch=master
+[downloads-image]: https://img.shields.io/npm/dm/unpipe.svg
+[downloads-url]: https://npmjs.org/package/unpipe