refactor(nix): split formatter and app outputs

src/dotfiles/default.nix

@@ -3,6 +3,7 @@
   inputs,
   self,
   root,
+  system,
 }:
 let
   util = import ./util.nix { inherit lib; };
@@ -38,18 +39,22 @@ let
       ;
     registry = registry.collected;
   };
+
+  formatter = import ./formatter.nix {
+    inherit inputs system;
+  };
 in
 {
-  inherit
-    (import ./apps.nix {
-      inherit
-        inputs
-        lib
-        ;
-    })
-    apps
-    formatter
-    ;
+  formatter.${system} = formatter;
+
+  apps.${system} = import ./apps.nix {
+    inherit
+      inputs
+      lib
+      formatter
+      system
+      ;
+  };
 
   nixosConfigurations = import ./hosts.nix {
     inherit