chore: 忽略根目录 air-cargo/，CLAUDE.md 声明其仅作另一仓库的提交通道

- .gitignore 新增 air-cargo/（同一份源码的独立 git 仓库，远程不同）
- CLAUDE.md 新增「air-cargo 目录：一律忽略」：扫描、开发、查历史均跳过，
  仅 sync-air-cargo skill 可操作

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -1,6 +1,8 @@
 # Created by https://www.toptal.com/developers/gitignore/api/androidstudio,gradle,java,kotlin
 # Edit at https://www.toptal.com/developers/gitignore?templates=androidstudio,gradle,java,kotlin
 
+air-cargo/
+
 ### Java ###
 # Compiled class file
 *.class