@ file autocomplete not showing any files

Bug Description:
When typing '@' to reference files in the chat, no autocomplete suggestions appear.

Environment:

• macOS (Darwin 25.1.0)
• Directory has multiple files that should be suggested
• Not related to .gitignore

Expected:
After typing '@', should see list of files for autocomplete selection

Actual:
No suggestions appear

Reproducible:
Yes, consistently in current session