Make Emacs flake standalone

flakes/emacs/flake.nix

@@ -1,15 +1,55 @@
 {
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-    home-manager.url = "github:nix-community/home-manager/";
-    home-manager.inputs.nixpkgs.follows = "nixpkgs";
-  };
+  description = "Standalone Tobmacs package and NixOS integration";
 
-  outputs = inputs:
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems = [
+        "aarch64-darwin"
+        "aarch64-linux"
+        "x86_64-linux"
+      ];
+      forAllSystems = nixpkgs.lib.genAttrs systems;
+    in
     {
+      packages = forAllSystems (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+            config.allowUnfreePredicate = package:
+              builtins.elem (nixpkgs.lib.getName package) [
+                "copilot-language-server"
+              ];
+          };
+        in
+        {
+          default = import ./package.nix { inherit pkgs; };
+          tobs-emacs = self.packages.${system}.default;
+        });
+
+      apps = forAllSystems (system: {
+        default = {
+          type = "app";
+          program = "${self.packages.${system}.default}/bin/emacs";
+          meta.description = "Run Tobmacs";
+        };
+      });
+
+      # Importing this module selects Tobmacs as services.emacs.package. The
+      # caller still decides whether to enable or merely install the service.
+      nixosModules.default = { pkgs, ... }: {
+        services.emacs.package =
+          self.packages.${pkgs.stdenv.hostPlatform.system}.default;
+      };
+
+      # Optional compatibility integration for this dotfiles repository. The
+      # standalone package and NixOS module above do not depend on Home Manager.
       homeManagerModules = {
-        aarch64-darwin = import ./home.nix;
-        x86_64-linux = import ./home.nix;
+        default = import ./home.nix { inherit self; };
+        aarch64-darwin = self.homeManagerModules.default;
+        aarch64-linux = self.homeManagerModules.default;
+        x86_64-linux = self.homeManagerModules.default;
       };
     };
 }