refactor(core): display selected doc & attachment chip (#13443)

<img width="1275" height="997" alt="截屏2025-08-08 15 13 59"
src="https://github.com/user-attachments/assets/b429239d-84dc-490d-ad1e-957652e3caba"
/>


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced support for attachment chips in AI chat, allowing
individual attachments to be displayed, added, and removed as separate
chips.
* Added a new visual component for displaying attachment chips in the
chat interface.

* **Improvements**
* Enhanced chat composer to handle attachments and document chips
separately, improving clarity and control over shared content.
* Expanded criteria for triggering chat actions to include both document
and attachment selections.

* **Refactor**
* Updated context management to process attachments individually rather
than in batches, streamlining the addition and removal of context items.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->