feat(nixos): add nixos-hardware profiles for the x86 hosts

T400 gets the generic lenovo-thinkpad + common-pc-laptop(-ssd) +
common-cpu-intel blocks (no t400-specific profile exists); this also
enables tlp and the tp_smapi/acpi_call battery tooling. Mac Pro 3,1 gets
common-pc-ssd + common-cpu-intel. nixos-hardware follows our nixpkgs to
keep a single nixpkgs in the closure.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

flake.nix

@@ -54,6 +54,12 @@
       url = "github:nix-community/nixvim/nixos-26.05";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+    # Curated per-hardware profiles (microcode, SSD, platform quirks) for the
+    # physical x86 hosts.
+    nixos-hardware = {
+      url = "github:NixOS/nixos-hardware";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs =
@@ -232,6 +238,13 @@
             modules = [
               ./system/machine/T400/configuration.nix
               ./system/modules/laptop.nix
+              # No t400-specific profile exists; compose the generic ThinkPad +
+              # laptop/SSD/Intel building blocks (tp_smapi/acpi_call for battery
+              # thresholds, SSD + microcode defaults).
+              inputs.nixos-hardware.nixosModules.lenovo-thinkpad
+              inputs.nixos-hardware.nixosModules.common-pc-laptop
+              inputs.nixos-hardware.nixosModules.common-pc-laptop-ssd
+              inputs.nixos-hardware.nixosModules.common-cpu-intel
               ./lyrathorpe/swaywm.nix
             ];
             homeModules = [
@@ -248,6 +261,8 @@
             modules = [
               ./system/machine/MacPro31/configuration.nix
               ./system/modules/desktop.nix
+              inputs.nixos-hardware.nixosModules.common-pc-ssd
+              inputs.nixos-hardware.nixosModules.common-cpu-intel
               ./lyrathorpe/swaywm.nix
             ];
             homeModules = [