fix(frontend): 修复 Markdown 目录锚点跳转与 Tauri 路由

- 安装 rehype-slug 插件，自动为 heading 生成 id，解决目录链接无锚点目标的问题
- 自定义 <a> 组件处理内部锚点链接，阻止默认刷新行为并使用 scrollIntoView 平滑滚动
- Tauri 桌面端改用 HashRouter，避免刷新时 404 及错误打开外部浏览器

fixes #xxx

Co-Authored-By: HAPI <noreply@hapi.run>

BillNote_frontend/src/App.tsx

@@ -1,6 +1,6 @@
 import './App.css'
 import { lazy, Suspense, useEffect } from 'react'
-import { BrowserRouter, Navigate, Routes, Route } from 'react-router-dom'
+import { BrowserRouter, HashRouter, Navigate, Routes, Route } from 'react-router-dom'
 import { useTaskPolling } from '@/hooks/useTaskPolling.ts'
 import { useCheckBackend } from '@/hooks/useCheckBackend.ts'
 import { systemCheck } from '@/services/system.ts'
@@ -57,12 +57,16 @@ function App() {
     )
   }
 
+  // 桌面端使用 HashRouter 避免刷新 404；Web 端继续使用 BrowserRouter
+  const isTauri = typeof window !== 'undefined' && '__TAURI_INTERNALS__' in window
+  const Router = isTauri ? HashRouter : BrowserRouter
+
   // 后端已初始化，渲染主应用
   return (
     <>
       <StartupBanner />
       <BackendHealthIndicator />
-      <BrowserRouter>
+      <Router>
         <Suspense fallback={<div className="flex h-screen items-center justify-center">加载中…</div>}>
           <Routes>
             <Route path="/onboarding" element={<Onboarding />} />
@@ -86,7 +90,7 @@ function App() {
             </Route>
           </Routes>
         </Suspense>
-      </BrowserRouter>
+      </Router>
     </>
   )
 }

BillNote_frontend/src/pages/HomePage/components/MarkdownViewer.tsx

@@ -14,6 +14,7 @@ import 'react-medium-image-zoom/dist/styles.css'
 import gfm from 'remark-gfm'
 import remarkMath from 'remark-math'
 import rehypeKatex from 'rehype-katex'
+import rehypeSlug from 'rehype-slug'
 import 'katex/dist/katex.min.css'
 import 'github-markdown-css/github-markdown-light.css'
 import { ScrollArea } from '@/components/ui/scroll-area.tsx'
@@ -47,7 +48,7 @@ const steps = [
 ]
 
 const remarkPlugins = [gfm, remarkMath]
-const rehypePlugins = [rehypeKatex]
+const rehypePlugins = [rehypeKatex, rehypeSlug]
 
 /**
  * 构建 ReactMarkdown components 对象，baseURL 用于修正图片路径。
@@ -117,6 +118,31 @@ function createMarkdownComponents(baseURL: string) {
         )
       }
 
+      // 处理笔记内部锚点链接（如目录跳转）
+      if (href?.startsWith('#')) {
+        const handleAnchorClick = (e: React.MouseEvent) => {
+          e.preventDefault()
+          const id = decodeURIComponent(href.slice(1))
+          const target = document.getElementById(id)
+          if (target) {
+            target.scrollIntoView({ behavior: 'smooth', block: 'start' })
+          } else {
+            toast.error('未找到对应章节')
+          }
+        }
+
+        return (
+          <a
+            href={href}
+            onClick={handleAnchorClick}
+            className="text-primary hover:text-primary/80 inline-flex items-center gap-0.5 font-medium underline underline-offset-4"
+            {...props}
+          >
+            {children}
+          </a>
+        )
+      }
+
       return (
         <a
           href={href}