Design system, aesthetic direction, and copy voice guide for all Typster frontend work. Use this skill whenever the user is building, editing, reviewing, or extending any page or component in the Typster web app — landing page, app UI, marketing sections, new routes, or any .heex template or CSS. Also trigger when the user asks about tokens, copy, components, dark mode, animations, redesign direction, or wants to add a new section, page, or design pattern. When a new design decision is made, update the relevant guide doc to keep it current.