Add tablet landscape layout and allow PWA horizontal orientation.

Split mobile and tablet breakpoints, restore desktop-style reading on landscape tablets, and lock Android tablet apps to landscape.

Co-authored-by: Cursor <cursoragent@cursor.com>

.vitepress/theme/index.ts

@@ -1,12 +1,14 @@
 import DefaultTheme from 'vitepress/theme'
 import { h, defineComponent } from 'vue'
 import InstallApp from './InstallApp.vue'
+import { initTabletLandscape } from './tablet-landscape'
 import './custom.css'
 
 if (typeof window !== 'undefined') {
   import('virtual:pwa-register').then(({ registerSW }) => {
     registerSW({ immediate: true })
   })
+  initTabletLandscape()
 }
 
 /** 旧 markdown 的 <font> 标签改为 div，避免手机端布局溢出 */