paxx12-snapmaker-u1/SnapmakerU1-Extended-Firmware — reverse-engineered prompt

I want this project turned into a working buildable custom firmware setup for the Snapmaker U1 printer. The main goal is to build the firmware from source, keep the extra debug access like SSH, and preserve the added capabilities mentioned in the docs without changing the basic purpose of the project.

Please get the build flow working end to end, preferably the simplest way for someone to run it locally, and make sure it produces the firmware files a user would actually flash. If anything is missing or broken, fix it in place. Also leave me with clear, plain English instructions for how to build it, where the output ends up, and any important warnings about flashing custom firmware and warranty risk.

If there are docs or release notes that matter, use them to match the intended behavior. You can look up current docs online if needed. I do not need new features, I just want this repo cleaned up and working as a reliable custom firmware build for the U1.