Non-NixOS machines with just the Nix package manager installed have no
module system to pick up modules/nix-cache/client.nix, so this edits
/etc/nix/nix.conf directly (extra-substituters/extra-trusted-public-keys,
plus the SSH remote-builder config once the nixremote key is installed),
falling back to cache.nixos.org when nix-cache is unreachable.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
