feat(reference): 内嵌 claude-code 和 codex 文档作为 submodules

- 添加 claude-code-docs 和 codex 作为 git submodules
- 更新 tauri.conf.json 将文档打包到应用资源中
- 修改 Rust 后端支持从应用资源读取内嵌文档
- 用户自定义文档优先于内嵌文档

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: MarkShawn2020

.gitmodules

@@ -4,3 +4,9 @@
 [submodule "third-parties/claude-plugins-official"]
 	path = third-parties/claude-plugins-official
 	url = git@github.com:anthropics/claude-plugins-official.git
+[submodule "third-parties/claude-code-docs"]
+	path = third-parties/claude-code-docs
+	url = git@github.com:MarkShawn2020/claude-code-docs.git
+[submodule "third-parties/codex"]
+	path = third-parties/codex
+	url = git@github.com:openai/codex.git