feat: v0.2.4 — 搜索面板全面重设计 + 完整安装文档

### Changed
- 搜索面板：暗色玻璃拟态设计，SVG 图标，流畅动画，改进间距和焦点状态
- README / site：补全 npm / CDN / ESM / CJS / 浏览器五种安装方式

### Fixed
- CI 卡死：移除 setInterval，改用纯事件驱动
- 浮动工具栏定位修正
- 浮动工具栏开关按钮修复

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@metona-team/metona-editor",
-  "version": "0.2.3",
+  "version": "0.2.4",
   "description": "Type-safe, lightweight, zero-dependency Markdown Editor. Desktop-first. React-free. Single-file bundle.",
   "type": "module",
   "main": "dist/metona-editor.js",