AI Assistant tab doesn’t have a light theme icon

Steps to reproduce:
1. Create a new Unity project and make sure to have an AI Assistant installed
2. Make sure Editor theme is set to light
3. Open the AI Assistant window 
4. Observe the window tab icon

Actual results: AI Assistant icon is difficult to see in the window’s tab

Expected results: AI Assistant tab has a light theme icon and icon is visible

Reproducible with versions: 1.0.0-pre.8 (6000.2.0b10, 6000.3.0a2)

Tested on (OS): macOS Silicon, Sequoia 15.5 (M1)