refactor(nix): split formatter and app outputs

src/dotfiles/apps.nix

@@ -1,25 +1,16 @@
 {
   inputs,
   lib,
+  formatter,
+  system,
 }:
 let
-  system = "x86_64-linux";
   pkgs = inputs.nixpkgs.legacyPackages.${system};
 
-  treefmtEval = inputs.treefmt-nix.lib.evalModule pkgs {
-    projectRootFile = "flake.nix";
-
-    programs.nixfmt.enable = true;
-
-    settings.formatter.nixfmt.excludes = [
-      "configs/nixos/hosts/*/hardware-configuration.nix"
-    ];
-  };
-
   styleCheck = pkgs.writeShellApplication {
     name = "style-check";
     runtimeInputs = [
-      treefmtEval.config.build.wrapper
+      formatter
       pkgs.statix
       pkgs.deadnix
     ];
@@ -31,9 +22,7 @@ let
   };
 in
 {
-  formatter.${system} = treefmtEval.config.build.wrapper;
-
-  apps.${system}.style-check = {
+  style-check = {
     type = "app";
     program = lib.getExe styleCheck;
   };