Close [AI-301](https://linear.app/affine-design/issue/AI-301)
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **New Features**
* Introduced a new component for adding context (images, documents,
tags, collections) to AI chat via a plus button and popover menu.
* Added notification feedback for duplicate chip additions and image
upload limits.
* Chips panel now supports collapsing and expanding for improved UI
control.
* **Improvements**
* Refactored chip management for better error handling, feedback, and
external control.
* Streamlined image and document uploads through a unified menu-driven
interface.
* Enhanced chip management methods with clearer naming and robust
synchronization.
* Updated chat input to delegate image upload and context additions to
the new add-context component.
* **Bug Fixes**
* Improved cancellation and cleanup of ongoing chip addition operations
to prevent conflicts.
* **Tests**
* Updated end-to-end tests to reflect the new menu-driven image upload
workflow and removed legacy checks.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Co-authored-by: fengmk2 <fengmk2@gmail.com>
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