refactor(nixos): inline module enable conditions

configs/nixos/modules/desktop/session/waybar.nix

@@ -6,7 +6,6 @@
 }:
 # Waybar: a top status bar reading system state at a glance.
 let
-  cfg = config.modules.desktop.session.waybar; # NOLINT(let_order)
   vpnClient = config.modules.network.vpn-client;
 
   # A Nerd Font Private-Use-Area codepoint as a literal character, decoded
@@ -102,7 +101,7 @@ in
 {
   options.modules.desktop.session.waybar.enable = lib.mkEnableOption "the Waybar status bar";
 
-  config = lib.mkIf cfg.enable {
+  config = lib.mkIf config.modules.desktop.session.waybar.enable {
     # A symbols font backs the module glyphs, so pango falls back to it for the
     # codepoints Stylix's monospace font does not carry.
     fonts.packages = [ pkgs.nerd-fonts.symbols-only ];