feat(docs): enhance browser language auto-detection

Improve automatic language switching based on browser preferences:

- Use onBeforeMount for SSR compatibility with window check
- Add localStorage to remember user's language preference
- Save preference when user visits /en/ or /zh/ homepage
- Check current path to avoid unnecessary redirects
- Add missing link property to root locale config

This ensures:
1. First-time visitors are redirected based on browser language
2. Returning visitors go to their previously selected language
3. No infinite redirect loops occur

Author: shijiashuai

docs/.vitepress/config.ts

@@ -151,6 +151,7 @@ export default withMermaid(defineConfig({
     root: {
       label: 'English',
       lang: 'en-US',
+      link: '/en/',
       themeConfig: {
         nav: sharedNav('en'),
         sidebar: sharedSidebar['/en/'],

docs/en/index.md

@@ -14,6 +14,16 @@ hero:
       link: https://github.com/LessUp/compress-kit
 ---
 
+<script setup>
+import { onBeforeMount } from 'vue'
+
+onBeforeMount(() => {
+  if (typeof window !== 'undefined') {
+    localStorage.setItem('docs-lang-preference', '/en/')
+  }
+})
+</script>
+
 ## Quick Start
 
 ```bash

docs/index.md

@@ -14,15 +14,25 @@ hero:
 ---
 
 <script setup>
-import { onMounted } from 'vue'
+import { onBeforeMount } from 'vue'
 import { useRouter } from 'vitepress'
 
-onMounted(() => {
+// Client-only execution for SSR compatibility
+onBeforeMount(() => {
+  if (typeof window === 'undefined') return
+  
   const router = useRouter()
-  const lang = navigator.language || navigator.userLanguage
-  if (lang.startsWith('zh')) {
+  const userLang = navigator.language || navigator.userLanguage || ''
+  const savedLang = localStorage.getItem('docs-lang-preference')
+  
+  // Use saved preference if exists, otherwise use browser language
+  const targetLang = savedLang || (userLang.startsWith('zh') ? '/zh/' : '/en/')
+  const currentPath = window.location.pathname
+  
+  // Only redirect if not already on correct language path
+  if (targetLang === '/zh/' && !currentPath.startsWith('/zh')) {
     router.go('/zh/')
-  } else {
+  } else if (targetLang === '/en/' && !currentPath.startsWith('/en')) {
     router.go('/en/')
   }
 })

docs/zh/index.md

@@ -14,6 +14,16 @@ hero:
       link: https://github.com/LessUp/compress-kit
 ---
 
+<script setup>
+import { onBeforeMount } from 'vue'
+
+onBeforeMount(() => {
+  if (typeof window !== 'undefined') {
+    localStorage.setItem('docs-lang-preference', '/zh/')
+  }
+})
+</script>
+
 ## 快速开始
 
 ```bash