ci: validate docs mdx before publish

.github/workflows/docs-sync-publish.yml

@@ -43,6 +43,12 @@ jobs:
             --source-repo "$GITHUB_REPOSITORY" \
             --source-sha "$GITHUB_SHA"
 
+      - name: Install docs MDX checker dependency
+        run: npm install --no-save --package-lock=false @mdx-js/mdx@3.1.1
+
+      - name: Check publish docs MDX
+        run: node "$GITHUB_WORKSPACE/publish/.openclaw-sync/check-docs-mdx.mjs" "$GITHUB_WORKSPACE/publish/docs"
+
       - name: Commit publish repo sync
         working-directory: publish
         run: |