WSL is no longer used. This removes:
- machines/wixos/ directory and configuration.nix
- nixos-wsl input from flake.nix
- nixosConfigurations.wixos output
- References to wixos in AGENTS.md and .goosehints
Implements bead: nixos-configs-2mk
I'm standardizing on bitwarden and rbw for secrets. No need to build out
a separate secret management system. The complexity of this was just not
worth it for my effectively single-user workflows
