Textualize/textual ? reverse-engineered prompt

Build me a Python framework for making polished terminal apps that can also run in the browser.

I want a clean, simple API for building cross platform user interfaces with widgets like buttons, trees, data tables, inputs, text areas, and lists, plus a flexible layout system and a few nice default themes so apps look good right away. It should support things like a command palette, basic developer tooling for debugging apps from another terminal, and a solid testing setup so the framework is easy to maintain.

Please include a small demo app, a few example apps, and documentation that shows how to get started, how to build a clock style app, and how to serve an app in the browser. If you need to check current docs or patterns for anything, look them up online.