Rewrite README tone and structure

[yitianlian]

Summary

• rewrite the English and Chinese READMEs in a less slogan-heavy, more repository-oriented style
• foreground what the repo is, how to use it, and what files matter
• keep the quick start accurate while reducing list-heavy marketing language
• preserve acknowledgements and citation info in a cleaner structure

Reference style

• reviewed README structures from OpenHands, aider, and RepoAgent for layout and pacing
• rewrote this README to be more direct and easier to scan

Validation

• re-ran the quick-start skill listing commands
• verified .agents/skills and .claude/skills still list matching skills