bug: File-attachment overlay for '@' does not disappear after typing the next word

Hello,

I discovered that in the conversational context, typing @ (which is meant for attaching a file) leaves the file-selection overlay stuck open. It does not close even after continuing to type the next word, and the page must be reloaded to get rid of it.

Steps to reproduce:

1. Open a conversation in Open Computer.
2. Type @ in the message input to trigger the file-attachment overlay.
3. Continue typing the next word (e.g. @inject funktioniert nicht).
4. Observe that the overlay (showing "No files found") remains visible.
5. Try to dismiss the overlay. It never disappears and the only workaround is reloading the page.

Expected behavior:
The file-attachment overlay should hide as soon as the @ mention no longer applies (e.g. when the next word is typed), without requiring a page reload.

A screenshot of the stuck overlay is attached for reference.

Thank you in advance for looking into this!

Best regards,
Joshua Krimmer

Start by reproducing the issue in the conversation message input, then trace the file-attachment overlay triggered by @ and how it responds when the next word is typed. Done means the overlay closes when the @ mention no longer applies without requiring a page reload.