Generate production-quality colorful icon sets using Google Imagen 4. Use this skill when the user needs custom app icons, emoji-style icons, cartoon icons, or any colorful icon set. Takes a project description, suggests icons, generates 1024px PNGs via Imagen 4, removes backgrounds, downscales to all target sizes, and delivers a review gallery for iterative refinement. Trigger on: "icon set", "generate icons", "app icons", "custom icons", "colorful icons", "cartoon icons", "emoji icons", "make icons", "icon generation", "imagen icons", or any request for a set of colorful visual assets.