Scaffolds a site-local theme from an official one.

Usage

mix cherry.gen.theme NAME [--from THEME] [--source DIR] [--json]

Copies the official theme (--from default, or cherrybomb) into themes/NAME/ — manifest, templates, stylesheet, islands — and renames it. Point cherry.exs at it with theme: "themes/NAME" and every file is yours; the swap contract keeps the site building throughout.