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

dist/metona-editor.d.ts

@@ -507,7 +507,7 @@ declare const animationUtils: {
     destroy(): void;
 };
 
-declare const VERSION = "0.2.3";
+declare const VERSION = "0.2.4";
 declare function create(container: string | HTMLElement, options?: EditorOptions): MarkdownEditor;
 declare function use(plugin: string | any, options?: any): typeof api;
 declare function on(name: string, fn: (editor: MarkdownEditor) => void): () => void;