Close [AI-331](https://linear.app/affine-design/issue/AI-331)
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## Summary by CodeRabbit
* **Improvements**
* Session history now displays the session title (or "New chat" if
unavailable) instead of the session ID for a clearer user experience.
* **Performance**
* Recent copilot chat session lists now load faster by excluding message
details from the initial query.
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