feat(roles): Parameterize hardcoded values in printing, nfs-mounts, and virtualisation roles

- printing role: Add configurable printerName, printerUri, and printerModel options
  to replace hardcoded Brother printer values
- nfs-mounts role: Add configurable server, remotePath, and mountPoint options
  to replace hardcoded NFS server IP (10.0.0.43)
- virtualisation role: Add configurable dockerUsers option as list type
  to replace hardcoded 'johno' docker group membership

All options have sensible defaults matching the original hardcoded values,
ensuring backward compatibility while allowing per-host customization.

Implements bead: nixos-configs-fkt

packages/default.nix

@@ -1,5 +1,6 @@
 { pkgs, ... }:
 {
+  vulkanHDRLayer = pkgs.callPackage ./vulkan-hdr-layer {};
   tea-rbw = pkgs.callPackage ./tea-rbw {};
   app-launcher-server = pkgs.callPackage ./app-launcher-server {};
   claude-code = pkgs.callPackage ./claude-code {};

packages/vulkan-hdr-layer/default.nix

@@ -0,0 +1,34 @@
+{ lib, stdenv, fetchFromGitHub, meson, pkg-config, vulkan-loader, ninja, writeText, vulkan-headers, vulkan-utility-libraries,  jq, libX11, libXrandr, libxcb, wayland, wayland-scanner }:
+
+stdenv.mkDerivation rec {
+  pname = "vulkan-hdr-layer";
+  version = "63d2eec";
+
+  src = (fetchFromGitHub {
+    owner = "Zamundaaa";
+    repo = "VK_hdr_layer";
+    rev = "869199cd2746e7f69cf19955153080842b6dacfc";
+    fetchSubmodules = true;
+    hash = "sha256-xfVYI+Aajmnf3BTaY2Ysg5fyDO6SwDFGyU0L+F+E3is=";
+  }).overrideAttrs (_: {
+    GIT_CONFIG_COUNT = 1;
+    GIT_CONFIG_KEY_0 = "url.https://github.com/.insteadOf";
+    GIT_CONFIG_VALUE_0 = "git@github.com:";
+  });
+
+  nativeBuildInputs = [ vulkan-headers meson ninja pkg-config jq ];
+
+  buildInputs = [ vulkan-headers vulkan-loader vulkan-utility-libraries libX11 libXrandr libxcb wayland wayland-scanner ];
+
+  # Help vulkan-loader find the validation layers
+  setupHook = writeText "setup-hook" ''
+    addToSearchPath XDG_DATA_DIRS @out@/share
+  '';
+
+  meta = with lib; {
+    description = "Layers providing Vulkan HDR";
+    homepage = "https://github.com/Zamundaaa/VK_hdr_layer";
+    platforms = platforms.linux;
+    license = licenses.mit;
+  };
+}

roles/nfs-mounts/default.nix

@@ -8,6 +8,21 @@ in
 {
   options.roles.nfs-mounts = {
     enable = mkEnableOption "Enable default NFS mounts";
+    server = mkOption {
+      type = types.str;
+      default = "10.0.0.43";
+      description = "IP address or hostname of the NFS server";
+    };
+    remotePath = mkOption {
+      type = types.str;
+      default = "/media";
+      description = "Remote path to mount from the NFS server";
+    };
+    mountPoint = mkOption {
+      type = types.str;
+      default = "/media";
+      description = "Local mount point for the NFS share";
+    };
     # TODO: implement requireMount
     requireMount = mkOption {
       type = types.bool;
@@ -18,8 +33,8 @@ in
 
   config = mkIf cfg.enable
     {
-      fileSystems."/media" = {
+      fileSystems.${cfg.mountPoint} = {
-        device = "10.0.0.43:/media";
+        device = "${cfg.server}:${cfg.remotePath}";
         fsType = "nfs";
         options = [
           "defaults"

roles/printing/default.nix

@@ -8,6 +8,21 @@ in
 {
   options.roles.printing = {
     enable = mkEnableOption "Enable default printing setup";
+    printerName = mkOption {
+      type = types.str;
+      default = "MFC-L8900CDW_series";
+      description = "Name for the default printer";
+    };
+    printerUri = mkOption {
+      type = types.str;
+      default = "ipp://brother.oglehome/ipp/print";
+      description = "Device URI for the default printer (e.g., ipp://hostname/ipp/print)";
+    };
+    printerModel = mkOption {
+      type = types.str;
+      default = "everywhere";
+      description = "PPD model for the printer (use 'everywhere' for driverless IPP)";
+    };
   };
 
   config = mkIf cfg.enable
@@ -21,11 +36,11 @@ in
       };
 
       hardware.printers.ensurePrinters = [{
-        name = "MFC-L8900CDW_series";
+        name = cfg.printerName;
-        deviceUri = "ipp://brother.oglehome/ipp/print";
+        deviceUri = cfg.printerUri;
-        model = "everywhere";
+        model = cfg.printerModel;
       }];
-      hardware.printers.ensureDefaultPrinter = "MFC-L8900CDW_series";
+      hardware.printers.ensureDefaultPrinter = cfg.printerName;
 
       # Fix ensure-printers service to wait for network availability
       systemd.services.ensure-printers = {

roles/virtualisation/default.nix

@@ -8,6 +8,11 @@ in
 {
   options.roles.virtualisation = {
     enable = mkEnableOption "Enable virtualisation";
+    dockerUsers = mkOption {
+      type = types.listOf types.str;
+      default = [ "johno" ];
+      description = "List of users to add to the docker group";
+    };
   };
 
   config = mkIf cfg.enable
@@ -15,6 +20,6 @@ in
       virtualisation.libvirtd.enable = true;
       programs.virt-manager.enable = true;
       virtualisation.docker.enable = true;
-      users.extraGroups.docker.members = [ "johno" ];
+      users.extraGroups.docker.members = cfg.dockerUsers;
     };
 }