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

03_install/3.6_offline.md

@@ -8,11 +8,11 @@
 
 ![Docker-offile-install-top](../_images/image-20200412202617411.png)
 
-### 概述
+### 3.6.1 概述
 
 总体概述了以下内容。
 
-### CentOS/Rocky/AlmaLinux 离线安装 Docker
+### 3.6.2 CentOS/Rocky/AlmaLinux 离线安装 Docker
 
 在无法连接外网的安全环境中，离线安装是唯一的选择。本节介绍如何在 RHEL 系发行版中进行离线安装。