This is a neat idea. It opens up a whole new way to make a web app into a native app, while also adding native features not available in web views

I have a working (and not vibe coded) implementation of a "browser engine for apps": https://github.com/DioxusLabs/blitz

So far it's only HTML/CSS (and we have our Rust-based framework to write the apps in). But it has been designed for fast incremental rendering, so it could be extended with JavaScript support quite easily.