[Feature] Add GEMINI.md and AGENTS.md

[flowKKo]

🥰 需求描述 | Feature Description

当前项目缺少gemini-cli和codex的全局指导markdown文件。我们可以加上这些文件

The current project lacks global guidance markdown files for gemini-cli and codex. We can add these files

🧐 解决方案 | Proposed Solution

将CLAUDE.md中的内容抽离到文件AI_GUIDE.md中，在这里维护对AI编程工具的指导内容。接着实现一个根据AI_GUIDE.md中的内容来自动创建含有对应内容的GEMINI.md，AGENTS.md和CLAUDE.md的脚本。后续用户只要修改AI_GUIDE.md中的内容，再运行bun run generate:ai-guides就能够同步修改这些指导文件的内容

Extract the content from CLAUDE.md into a file called AI_GUIDE.md, where we'll maintain guidance content for AI programming tools. Then implement a script that automatically creates GEMINI.md, AGENTS.md, and CLAUDE.md with corresponding content based on AI_GUIDE.md. Going forward, users only need to modify the content in AI_GUIDE.md and run bun run generate:ai-guides to synchronize changes across these guidance files.

[flowKKo]

Next Step

Update the content in AI_GUIDE.template.md to match the current project content. Let AI obtain more comprehensive and accurate global context

[flowKKo]

I've modified the content of AI_GUIDE.template.md in PR #150. I shortened and reorganized the content based on how popular AI Agent repositories structure their agent instructions. Please check the PR for details.