refactor: Fleet and sw behind mkIf guards

sw/ghostty.nix

@@ -1,4 +1,6 @@
 {
+  config,
+  lib,
   pkgs,
   ...
 }:
@@ -10,7 +12,11 @@
 # It reconstructs the terminfo database from the provided definition and
 # adds it to the system packages.
 
+with lib;
+
 let
+  cfg = config.athenix.sw;
+
   ghostty-terminfo = pkgs.runCommand "ghostty-terminfo" { } ''
     mkdir -p $out/share/terminfo
     cat > ghostty.info <<'EOF'
@@ -99,5 +105,7 @@ let
   '';
 in
 {
-  environment.systemPackages = [ ghostty-terminfo ];
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ ghostty-terminfo ];
+  };
 }