tamagui/tamagui ? reverse-engineered prompt

Build me a polished starter for a cross platform React app that shares the same UI on web and native.

I want a clean demo experience with a home screen, a few reusable components like buttons, cards, forms, and a simple settings page, all styled with a modern design system. It should feel fast on the web and work well on React Native too, with responsive layouts, light and dark themes, and nice spacing and typography. If it makes sense, use the project’s built in styling approach so components can be shared without extra work, and set things up so the app is easy to extend later.

Please make it look production ready, include sensible defaults, and wire up any basic docs or example usage needed so I can understand how to add my own screens and components. Look up current docs online if you need to.