♻️ refactor layout, simplify flake.nix

nix/shells.nix

@@ -0,0 +1,27 @@
+{ system, self, ... }:
+
+with self.pkgs.${system};
+
+let
+  darwin-local = writeScriptBin "darwin-local" ''
+    #!${stdenv.shell}
+    nix build .#darwinConfigurations.$(hostname -s).system
+    ./result/sw/bin/darwin-rebuild switch --flake .
+  '';
+in
+{
+  default = mkShell {
+    name = "athens";
+    buildInputs = with pkgs; [
+      darwin-local
+      deploy-rs.deploy-rs
+      deadnix
+      nil
+      nixpkgs-fmt
+      statix
+      sops
+    ];
+
+    inherit (self.checks.${system}.pre-commit-check) shellHook;
+  };
+}