[Bug] The "Delete agent" button is invisible when matching to system light theme

**Describe the bug**
I just installed Buzz and tried to delete an agent but you can't see the button. I switched my system to dark theme and then the button became visible. See the attached screenshot.

**Supporting Material**
see attached screenshot

**Environment (please complete the following information):**
- OS: MacOS 26.6 Beta
- Version

**Additional context**
I had Fable create a fix and I built from source and everything worked, but didn't want to contribute AI code as I figured y'all could provide a cleaner fix.

https://github.com/carimura/buzz/pull/1

Start by reproducing the deletion flow with the system set to the light theme on macOS, then inspect the Delete agent button's UI implementation. Done means the button is visible and usable when matching the light theme without regressing its appearance in dark theme.

Written by the indexing model from the issue text.