"Settings" icon doesn't adapt to the Light theme in the Mesh Generator

How to reproduce:
1. Open the project and install the AI Assistant
2. In Unity toolbar, AI -> Generate New -> 3D Object
3. Observe the "Settings" icon

Expected results: The "Settings" icon matches the Editor theme
Actual results: The "Settings" icon doesn't match the Editor theme

Reproducible with: 2.7.0-pre.3 (6000.6.0a4), 2.8.0-pre.1 (6000.0.75f1)

Reproducible on: macOS Tahoe 26 (M1)
Not reproducible on: No other environment tested