nomads-cloud and grib2json are only realwallpaper dependencies; they are
pulled in by path since pkgs/ is not an overlay.

pairprogramming, radio, realwallpaper and the htgen users no longer get
their ids from stockholm's genid. NixOS keeps the ids existing users
already have in /etc/passwd and /etc/group, so nothing changes on
deployed machines; fresh installs allocate them.

The copied htgen, reaktor2 and realwallpaper modules use nixpkgs option
types instead of stockholm's, htgen's user is a small name/home
submodule (home still defaults to /home/<name>), and reaktor2 carries
its own stripAttr.