folded t480 hardware config into the flake to get rid of --impure

modules/hosts/t480/default.nix

@@ -5,19 +5,10 @@
 }: {
   flake.nixosConfigurations.t480 = inputs.nixpkgs.lib.nixosSystem {
     modules = with self.nixosModules; [
-      # TODO: still importing by absolute path, so evaluating t480 requires
-      # --impure and picks up the hardware file of whatever machine you build
-      # from (on shadow, that means shadow's disk UUIDs — wrong but harmless
-      # until you actually deploy). Fix by running, ON THE T480 ITSELF:
-      #
-      #   nix run .#sync-hardware
-      #
-      # then create modules/hosts/t480/disks.nix (mirroring shadow's) and swap
-      # this line for `./_hardware.nix` + `t480Disks`. Cannot be done remotely:
-      # the hardware scan has to happen on the target machine.
-      /etc/nixos/hardware-configuration.nix
-      desktop
+      ./_hardware.nix
+      t480Disks
       t480Configuration
+      desktop
       # CPU microcode + integrated Intel GPU. The T480 also has an NVIDIA MX150;
       # to enable it in PRIME offload mode, swap gpuIntel for gpuNvidiaPrime
       # (which includes gpuIntel). Left on Intel-only by default to save power.