docs: improve generated llms.txt summaries (#335)

Author: ScriptedAlchemy

website/docs/en/guide/cli/doc.mdx

@@ -1,3 +1,7 @@
+---
+description: 'Develop, build, and preview Rspress documentation sites with the rs doc command.'
+---
+
 # doc
 
 import { PackageManagerTabs } from '@rspress/core/theme';

website/docs/en/guide/formatting.mdx

@@ -1,3 +1,7 @@
+---
+description: 'Format files with Rstack CLI using Prettier-compatible options, plugins, parallel formatting, and a persistent cache.'
+---
+
 # Formatting
 
 import { PackageManagerTabs } from '@rspress/core/theme';

website/docs/zh/guide/cli/doc.mdx

@@ -1,3 +1,7 @@
+---
+description: '使用 rs doc 命令开发、构建和预览 Rspress 文档站点。'
+---
+
 # doc
 
 import { PackageManagerTabs } from '@rspress/core/theme';

website/docs/zh/guide/formatting.mdx

@@ -1,3 +1,7 @@
+---
+description: '使用 Rstack CLI 格式化文件，支持与 Prettier 兼容的选项、插件、并行格式化和持久化缓存。'
+---
+
 # 格式化 \{#formatting}
 
 import { PackageManagerTabs } from '@rspress/core/theme';