Yeah, running just gpui is kinda like writing a react app without a component library. It is going to be on you to implement all your components.
All of those are handled. Run the "story" app. It is very impressive IMO.
Components list: https://longbridge.github.io/gpui-component/docs/components/
I'm not sure about that analogy: HTML provides the basic components atombender laments are missing from GPUI.
Thank you, that looks very promising indeed.