docs(readme): adjust the readme structure and add some note

[sl-gn]

📋 PR Title Format

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type(scope): concise message (max 50 chars)

Where:

• type is one of: feat, fix, docs, refactor, perf, test, chore.
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📝 Change Type

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• feat: New feature.
• fix: Bug fix.
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• test: Adding missing tests or correcting existing tests.
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💡 Description

Briefly describe the change, its purpose, and the problem it solves.

Key Changes

1. Adjust the readme structure, splitting the install and quick start sections.
2. add kimi k2 thinking and oss gpt safeguard description
3. add note to describe how to disable think in api request

🔗 Related Issues

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• Closes #IssueNumber (e.g., Closes #123)

✅ Checklist

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• I have performed a self-review of my own code.
• I have added/updated tests that prove my fix or feature works (if applicable).
• I have updated the documentation (if necessary).
• My code follows the project's style guidelines.