users: use launchctl managername to determine session type

Seems like this should be more robust, and it will work even
after the activation script purifies its environment. Apparently
it may treat `tmux` sessions like SSH ones, which may have
something to do with `reattach-to-user-namespace`/`pam_reattach`; see
<ChrisJohnsen/tmux-MacOSX-pasteboard#78 (comment)>.
(My hope is that `pam_reattach` does the right thing here, but I
haven’t tested.)

modules/users/default.nix

@@ -147,7 +147,7 @@ in
         homeDirectory=''${homeDirectory#NFSHomeDirectory: }
 
         if ! dscl . -change /Users/nobody NFSHomeDirectory "$homeDirectory" "$homeDirectory" &> /dev/null; then
-          if [[ -n "$SSH_CONNECTION" ]]; then
+          if [[ "$(launchctl managername)" != Aqua ]]; then
             printf >&2 '\e[1;31merror: users cannot be %s over SSH without Full Disk Access, aborting activation\e[0m\n' "$2"
             printf >&2 'The user %s could not be %s as `darwin-rebuild` was not executed with Full Disk Access over SSH.\n' "$1" "$2"
             printf >&2 'You can either:\n'