refactor(nix): simplify forAllSystems

flake.nix

@@ -17,6 +17,7 @@
       rust-overlay,
     }:
     let
+      inherit (nixpkgs) lib;
       systems = [
         "x86_64-linux"
         "aarch64-linux"
@@ -24,10 +25,16 @@
         "aarch64-darwin"
       ];
 
-      forAllSystems = fn: nixpkgs.lib.genAttrs systems (system: fn nixpkgs.legacyPackages.${system});
+      forAllSystems = lib.genAttrs systems;
+      nixpkgsFor = nixpkgs.legacyPackages;
+    in
+    {
+      devShells = forAllSystems (
+        system:
+        let
+          pkgs = nixpkgsFor.${system};
         in
         {
-      devShells = forAllSystems (pkgs: {
           default = pkgs.mkShell {
             packages = with pkgs; [
               redis
@@ -43,7 +50,6 @@
 
               # nix tools
               self.formatter.${system}
-            deadnix
               nil
               statix
             ];
@@ -51,20 +57,17 @@
             inputsFrom = [ self.packages.${pkgs.system}.refraction ];
             RUST_SRC_PATH = "${pkgs.rustPlatform.rustLibSrc}";
           };
-      });
+        }
+      );
 
-      formatter = forAllSystems (pkgs: pkgs.nixfmt-rfc-style);
+      formatter = forAllSystems (system: nixpkgsFor.${system}.nixfmt-rfc-style);
 
       nixosModules.default = import ./nix/module.nix self;
 
       packages = forAllSystems (
-        {
-          lib,
-          pkgs,
-          system,
-          ...
-        }:
+        system:
         let
+          pkgs = nixpkgsFor.${system};
           packages' = self.packages.${system};
 
           mkStatic = pkgs.callPackage ./nix/static.nix {