pn02: blacklist amdgpu kernel module for stability testing

pn02 continues to hard freeze with no log evidence. Blacklisting
the GPU driver to eliminate GPU/PSP firmware interactions as a
possible cause. Console output will be lost but the host is
managed over SSH.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hosts/pn02/configuration.nix

@@ -13,6 +13,7 @@
 
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
+  boot.blacklistedKernelModules = [ "amdgpu" ];
 
   networking.hostName = "pn02";
   networking.domain = "home.2rjus.net";