feat(neogaia): adopt the upstream hardware profile (task 0013)

The laptop's hardware facts were guessed before it ran NixOS. Hand them to
the upstream nixos-hardware profile for this exact model, which fixes four
things that are wrong on the running machine: the laptop suspends into
s2idle rather than deep S3, the PS/2 mouse driver loads over an i2c
touchpad, no thermal management runs, and firmware updates are impossible.

The profile is taken wholesale, including the Intel graphics support it
carries. Those packages are inert without a display server, and trimming
them would mean diverging from upstream for no present benefit.

Drop the host's own Intel microcode setting, which the profile now defaults
from the redistributable firmware already enabled here.

The input follows the base nixpkgs: only its NixOS modules are consumed, so
its own pin would be evaluated by nothing while drifting silently.

The two acceptance criteria needing a reboot are left open; the sleep mode
and module blacklist only take effect on a fresh boot.

hosts/neogaia/default.nix

@@ -1,8 +1,9 @@
-{ pkgs, ... }:
+{ inputs, pkgs, ... }:
 # neogaia — Dell XPS 13 9380 laptop.
 # Disk layout is in ./disk.nix; `fileSystems` are derived from it, none declared here.
 {
   imports = [
+    inputs.nixos-hardware.nixosModules.dell-xps-13-9380
     ./hardware-configuration.nix
     ./disk.nix
   ];
@@ -15,9 +16,8 @@
 
   boot.kernelPackages = pkgs.linuxPackages_cachyos;
 
-  hardware.cpu.intel.updateMicrocode = true;
-
   # Redistributable firmware for the QCA6174 wifi (ath10k blobs).
+  # Intel microcode updates follow from this; none declared here.
   hardware.enableRedistributableFirmware = true;
 
   # RAM-backed swap; no on-disk swap partition.