feat(nixos): replace X1 with ThinkPad T400; add Mac Pro 3,1 desktop

- lyrathorpe-t400 replaces lyrathorpe-x1c: ThinkPad T400 (legacy BIOS -> GRUB,
  Intel microcode + redistributable firmware for iwlwifi, pipewire, sshd).
- lyrathorpe-macpro31: new desktop host (portable = false) importing
  desktop.nix. Mac Pro 3,1 has 64-bit EFI -> systemd-boot; wired NetworkManager
  via desktop.nix; desktop status bar (temperature + net, no battery).

Both ship hand-written placeholder hardware-configuration.nix (root/swap/ESP by
label, GRUB device /dev/sda) to be regenerated with nixos-generate-config and
committed at install time. All five host configs evaluate; nixfmt clean.

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

flake.nix

@@ -192,12 +192,12 @@
             ];
           };
 
-          lyrathorpe-x1c = {
+          lyrathorpe-t400 = {
             system = "x86_64-linux";
             username = "lyrathorpe";
             fullName = "Lyra Thorpe";
             modules = [
-              ./system/machine/X1/configuration.nix
+              ./system/machine/T400/configuration.nix
               ./system/modules/laptop.nix
               ./lyrathorpe/swaywm.nix
             ];
@@ -207,6 +207,22 @@
             ];
           };
 
+          lyrathorpe-macpro31 = {
+            system = "x86_64-linux";
+            username = "lyrathorpe";
+            fullName = "Lyra Thorpe";
+            portable = false;
+            modules = [
+              ./system/machine/MacPro31/configuration.nix
+              ./system/modules/desktop.nix
+              ./lyrathorpe/swaywm.nix
+            ];
+            homeModules = [
+              ./lyrathorpe/home
+              ./lyrathorpe/home/desktop.nix
+            ];
+          };
+
           emmathorpe-edaas = {
             system = "x86_64-linux";
             username = "emmathorpe";