fix(i18n): 修复 VitePress 文档默认语言为中文

统一文档首页语言检测逻辑与 Landing Page 一致：
- 默认语言从英文改为中文
- 优先级：URL 参数 > localStorage > 浏览器语言 > 默认中文

Author: LessUp

docs/index.md

@@ -9,21 +9,34 @@ import { useRouter } from 'vitepress'
 onMounted(() => {
   const router = useRouter()
 
-  // 优先级：localStorage > URL 参数 > 浏览器语言
+  // 优先级：URL 参数 > localStorage > 浏览器语言 > 默认中文
   // 与 Landing Page (src/lib/i18n.ts) 保持一致
   const stored = localStorage.getItem('preferred-lang')
   const params = new URLSearchParams(window.location.search)
   const urlLang = params.get('lang')
+  const browserLang = navigator.language || navigator.userLanguage || ''
 
-  let targetLang = 'en'
-  if (urlLang === 'zh' || stored === 'zh-CN' || stored === 'zh') {
+  let targetLang = 'zh' // 默认中文
+
+  // 1. URL 参数（最高优先级）
+  if (urlLang === 'zh') {
+    targetLang = 'zh'
+  } else if (urlLang === 'en') {
+    targetLang = 'en'
+  }
+  // 2. localStorage（用户偏好）
+  else if (stored === 'zh-CN' || stored === 'zh') {
+    targetLang = 'zh'
+  } else if (stored === 'en') {
+    targetLang = 'en'
+  }
+  // 3. 浏览器语言
+  else if (browserLang.startsWith('zh')) {
     targetLang = 'zh'
-  } else if (urlLang === 'en' || stored === 'en') {
+  } else if (/^en/i.test(browserLang)) {
     targetLang = 'en'
-  } else {
-    const browserLang = navigator.language || navigator.userLanguage || ''
-    if (browserLang.startsWith('zh')) targetLang = 'zh'
   }
+  // 4. 默认中文（已设置）
 
   router.go(`/${targetLang}/`)
 })