AI app adds Gemma 4 compare mode

The useful part here is not just exposing more models, but making differences in output easy to see without forcing every user into a model-selection workflow.

• –Side-by-side runs make differences in structure, tone, and consistency obvious fast.
• –Keeping compare mode optional avoids turning the UI into a model picker first and an assistant second.
• –This is a practical pattern for teams choosing models per task instead of standardizing blindly on one default.
• –The real value is less "which model wins" and more "which model fits this prompt and workflow."