bootloader, nvidia: simplify by using 6.12

Got a crash that led to my initrd apparently disappearing. After a trip
through the woes of nixos-enter, we're back! In light of this, let's
*not* pull in the new nvidia drivers. We'll stick to 6.12, since I can't
get the drivers from unstable without re-evaluating nixpkgs to allow
unfree.

Anyways, if me or someone else needs it, here's the commands I used to
get nixos-enter working. The wiki was very little help (surprise), but
this guide was super useful:
https://www.adyxax.org/blog/2023/11/13/recovering-a-nixos-installation-from-a-linux-rescue-image/
```bash
sudo mount /dev/nvmeblahblah2 /mnt
cd /mnt
sudo mount /dev/nvme0n1p6 boot

// Maybe required, idk
sudo mount -o bind /dev /mnt/dev
sudo mount -o bind /proc /mnt/proc
sudo mount -o bind /sys /mnt/sys

// Probably not required
sudo chroot /mnt /nix/var/nix/profiles/system/activate # Wiki doesn't include the /system part

sudo nixos-enter
nix shell nixpkgs#git # Required for using flakes with nixos-rebuild
nixos-rebuild boot --flake /home/username/location/of/flake#hostname --option sandbox false # Might not need the sandbox
```

Author: llakala

config/core/bootloader.nix

@@ -7,7 +7,7 @@
     blacklistedKernelModules = [ ];
     extraModulePackages = with config.boot.kernelPackages; [  ];
     initrd.kernelModules = [ ];
-    kernelPackages = lib.mkDefault pkgs.linuxPackages_latest; # 6.13 breaking some stuff
+    kernelPackages = lib.mkDefault pkgs.linuxPackages_6_12; # 6.13 breaking some stuff on stable, see https://github.com/NixOS/nixpkgs/issues/375730#issuecomment-2625157971
 
     kernelParams = [ "boot.shell_on_fail" ]; # Open terminal environment if we fail to boot
   };

hosts/desktop/config/nvidia.nix

@@ -1,26 +1,7 @@
-{ config, ... }:
+{ inputs, lib, config, ... }:
 {
 
-  hardware.nvidia =
-  {
-    modesetting.enable = true;
+  imports = lib.singleton inputs.nixos-hardware.nixosModules.common-gpu-nvidia-nonprime;
 
-    powerManagement.enable = false;
-
-    powerManagement.finegrained = false;
-
-    open = false;
-    nvidiaSettings = true;
-
-package = config.boot.kernelPackages.nvidiaPackages.mkDriver {
-      version = "570.124.04";
-      sha256_64bit = "sha256-G3hqS3Ei18QhbFiuQAdoik93jBlsFI2RkWOBXuENU8Q=";
-      sha256_aarch64 = "sha256-KCGUyu/XtmgcBqJ8NLw/iXlaqB9/exg51KFx0Ta5ip0=";
-      openSha256 = "sha256-KCGUyu/XtmgcBqJ8NLw/iXlaqB9/exg51KFx0Ta5ip0=";
-      settingsSha256 = "sha256-LNL0J/sYHD8vagkV1w8tb52gMtzj/F0QmJTV1cMaso8=";
-      persistencedSha256 = "sha256-xctt4TPRlOJ685S52h5W6PT6/3Zy2R4ASNFPu8TSHKM=";
-    };
-  };
-
-  services.xserver.videoDrivers = ["nvidia"]; # Use proprietary drivers
+  hardware.nvidia.open = true;
 }