<img width="598" height="311" alt="Screenshot 2025-09-11 at 9 39 12 PM"
src="https://github.com/user-attachments/assets/b526e648-37cf-4412-83a0-42037b9fc94d"
/>

This is for both ACP and the regular agent. Previously we would always
include the whole file, which can easily blow the context window on huge
files.

Release Notes:

- When `@mention`ing large files, the Agent Panel now send an outline of
the file instead of the whole thing.