Token-based design system — the shared visual contract for every FE slice. Color / typography / spacing / motion tokens; component contracts; theming (light / dark / brand); Storybook + visual regression baseline. Lives between `wireframing-prototyping` (which uses the system) and `stack-web-frontend` (which implements it). Use whenever new tokens or components are being introduced, when wireframing requires a component not yet in the system, or when establishing the design language for a new product.
