GravitLauncher/Launcher — reverse-engineered prompt

Build me a usable Minecraft launcher from this Gravit based project, basically a cleaner and more polished version of the old sashok style launcher. I want it to feel like a real product people can open, log into, download the needed game files, pick the right client or server build if that is already supported here, and launch Minecraft without weird manual steps.

Please keep it grounded in what this repo already has instead of adding random extra features. If there is already a backend or API definition in the project, make the launcher work with that properly so the whole flow makes sense. I also want a simple local setup so I can run it, test it, and package it for actual use with clear instructions.

If the README is too thin, check the wiki or current docs online and fill in the missing setup details in a practical way that matches this codebase.