style(docs): standardize heading formats and numbering

- Enforce Level 1-3 structural numbering based on SUMMARY.md hierarchy
- Remove structural numbering from Level 4+ headings
- Eliminate single child headings by converting to bold text
- Auto-inject summary text for headings with multiple children missing intro text
- Exclude Appendix chapters from structural numbering
- Avoid modifying code block contents
- Add script to detect non-standard English usage in headers

01_introduction/summary.md

@@ -1,4 +1,4 @@
-## 本章小结
+## 1.4 本章小结
 
 - Docker 是一种轻量级虚拟化技术，核心价值是 **环境一致性**
 - 与虚拟机相比，Docker 更轻量、更快速、资源利用率更高