Close [AI-316](https://linear.app/affine-design/issue/AI-316)
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Chat status is now displayed and updated in the chat panel and
toolbar, allowing users to see when the chat is generating a response.
* The pin button in the chat toolbar is disabled while the chat is
generating a response, preventing pin actions during this time and
providing feedback via a notification if attempted.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
fe00293e3e