Theme gallery on cherrybomb.dev

LATER.md parked this "once a second+ theme exists" — the cherrybomb theme exists, so it's actionable. A page on cherrybomb.dev showing each official theme (screenshot in light/dark, token palette, `cherry config theme ` one-liner). Grows into a registry if third-party themes ever appear.

Start at the cherrybomb.dev site entry point and inspect how the existing theme is represented, including its light and dark views. Add a gallery covering each official theme with screenshots, token palettes, and the `cherry config theme ` command; done means the page is live and includes the currently official themes.

Written by the indexing model from the issue text.