docs: add sync-zh-en-docs skill

.agents/skills/sync-zh-en-docs/SKILL.md

@@ -0,0 +1,22 @@
+---
+name: sync-zh-en-docs
+description: Sync uncommitted docs between `website/docs/zh` and `website/docs/en`. Use when authors update docs in one language and need to align the mirrored `.md`/`.mdx` file in the other language.
+---
+
+# Sync Zh/En Documentation
+
+## Steps
+
+1. Check uncommitted changes under `website/docs/zh` and `website/docs/en`.
+
+2. Translate each changed file to the counterpart path (`zh` <-> `en`), and keep:
+
+- meaning and structure consistent
+- technical terms / commands / code blocks unchanged unless localization is required
+- concise, clear, professional technical-doc style
+
+3. Format and verify:
+
+```bash
+pnpm format
+```

website/README.md

@@ -6,6 +6,8 @@ This website is built with [Rspress](https://github.com/web-infra-dev/rspress),
 
 Currently Rsbuild provides documentation in English and Chinese. If you can use Chinese, please update both documents at the same time. Otherwise, just update the English documentation.
 
+You can use the local skill at [`sync-zh-en-docs`](../.agents/skills/sync-zh-en-docs/SKILL.md) to sync zh/en docs.
+
 ## Writing style guide
 
 The same as Rspack: [Writing style guide](https://github.com/web-infra-dev/rspack/tree/main/website#writing-style-guide).