Tailwind CSS v4 design system and styling vocabulary for Flutter — tokens, theming, and a typed utility API over the widgets layer. Changelog excerpt: - **Theme fonts now apply.** `FwTheme`applies the theme's `sans`family as the subtree's default text family, and `fontSans`/`fontSerif`/`fontMono`resolve to the active theme's families (like `roundedMd`/`shadowMd`do for radius/shadow) instead of generic names. A pasted/generated theme's fonts take effect once you register the font (bundle it or wire `google_fonts`). `font('Family')`remains a literal override. See the new **Fonts**docs page. - **New utilities:** `overline`(Tailwind `overline`text[...]