feat(flake, eat): remove flake-parts, add eat

flake.nix

@@ -2,35 +2,36 @@
   description = "Pankomacs";
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
-    parts = {
-      url = "github:hercules-ci/flake-parts";
-      inputs.nixpkgs-lib.follows = "nixpkgs";
-    };
     emacs = {
       url = "github:nix-community/emacs-overlay";
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
-  outputs = inputs:
-    inputs.parts.lib.mkFlake {
-      inherit inputs;
-    } {
+  outputs =
+    inputs:
+    let
+      inherit (inputs.nixpkgs) lib;
       systems = [
         "x86_64-linux"
       ];
-
-      imports = [
-        ./lib.nix
-      ];
-
-      perSystem = {pkgs, ...}: {
-        formatter = pkgs.alejandra;
-        packages = {
-          pgtk = inputs.self.lib.mkEmacs {
-            inherit pkgs;
-            emacs = pkgs.emacs30-pgtk;
+      forAllSystems = lib.genAttrs systems;
+      pkgs = builtins.listToAttrs (
+        map (system: {
+          name = system;
+          value = import inputs.nixpkgs {
+            inherit system;
           };
+        }) systems
+      );
+    in
+    {
+      lib = import ./lib.nix inputs;
+      formatter = forAllSystems (system: pkgs.${system}.nixfmt-rfc-style);
+      packages = forAllSystems (system: {
+        pgtk = inputs.self.lib.mkPankomacs {
+          pkgs = pkgs.${system};
+          emacs = pkgs.${system}.emacs30-pgtk;
         };
-      };
+      });
     };
 }