Ruixi-rebirth/flakes ? reverse-engineered prompt

Build me a personal NixOS flake setup that lets me install and manage a few different machine profiles from one repo.

I want a simple, reliable setup for a fresh NixOS install, plus a WSL based profile, and a fuller desktop profile for my main machine. Make the install path easy enough that I can clone the repo in a live environment, enter a dev shell, run disk setup, and then install the system without needing to figure out a lot of extra steps.

Please organize it so the common bits are shared, the host specific settings are kept separate, and secrets are handled safely. It should also include a convenient rebuild command for switching into the final configuration after the base install. Keep it practical and documented so I can follow the same flow on a new machine later, and look up current NixOS and flakes docs online if you need to.