gunter: switch to proprietary nvidia driver and load in initrd

The open nvidia driver had significant issues with DP MST displays,
including flip event timeouts and kernel warnings. The proprietary
driver handles MST failures more gracefully. Loading nvidia modules
in initrd eliminates the ~22 second black screen during boot.

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

hosts/gunter/configuration.nix

@@ -48,6 +48,12 @@
       memtest86.enable = true;
     };
     supportedFilesystems = [ "nfs" ];
+    initrd.kernelModules = [
+      "nvidia"
+      "nvidia_modeset"
+      "nvidia_uvm"
+      "nvidia_drm"
+    ];
   };
 
   # Networking stuff
@@ -86,7 +92,7 @@
     modesetting.enable = true;
     powerManagement.enable = false;
     powerManagement.finegrained = false;
-    open = true;
+    open = false;
     nvidiaSettings = false;
 
     package = config.boot.kernelPackages.nvidiaPackages.beta;