refactor(website): 优化网站内容以反映 core 模块实际功能

- 首页：更新核心功能展示（9个功能卡片），移除快速开始和 GitHub 链接
- 文档布局：移除 GitHub 链接
- 侧边栏：重组导航结构，分为「已完成功能」和「规划中功能」

packages/website/src/components/DocsSidebar.astro

@@ -10,28 +10,28 @@ const navigation = [
     title: '开始',
     items: [
       { title: '概览', href: '/docs' },
+      { title: '架构设计', href: '/docs/architecture' },
     ],
   },
   {
-    title: '架构设计',
-    items: [
-      { title: 'GUI Server/Client 架构', href: '/docs/architecture' },
-    ],
-  },
-  {
-    title: '功能设计',
+    title: '已完成功能',
     items: [
       { title: '编辑模式', href: '/docs/features/edit-modes' },
-      { title: '增强型仓库地图', href: '/docs/features/repo-map' },
+      { title: 'Checkpoint 系统', href: '/docs/features/checkpoint' },
       { title: '多模型支持', href: '/docs/features/multi-model' },
+      { title: '会话管理', href: '/docs/features/chat-history' },
+      { title: '仓库地图', href: '/docs/features/repo-map' },
+      { title: '浏览器 GUI', href: '/docs/features/browser-gui' },
+    ],
+  },
+  {
+    title: '规划中功能',
+    items: [
+      { title: '配置管理', href: '/docs/features/configuration' },
       { title: 'Linting 集成', href: '/docs/features/linting' },
       { title: '测试集成', href: '/docs/features/testing' },
-      { title: '对话历史管理', href: '/docs/features/chat-history' },
       { title: 'Watch 模式', href: '/docs/features/watch-mode' },
       { title: '语音输入', href: '/docs/features/voice-input' },
-      { title: '浏览器 GUI', href: '/docs/features/browser-gui' },
-      { title: '配置管理', href: '/docs/features/configuration' },
-      { title: 'Checkpoint 增强', href: '/docs/features/checkpoint' },
     ],
   },
 ];