Update to radiantave-cpp, enable plymouth boot image

flake.nix

@@ -5,7 +5,7 @@
     disko.inputs.nixpkgs.follows = "nixpkgs";
     nixos-facter-modules.url = "github:numtide/nixos-facter-modules";
     radiantwave.url = "git+https://gitea.radiantwavetech.com/RadiantWaveTech/radiantwave.git?ref=main";
-    radiantwave-dev.url = "git+https://gitea.radiantwavetech.com/RadiantWaveTech/radiantwave.git?ref=dev";
+    radiantwave-dev.url = "git+https://gitea.radiantwavetech.com/RadiantWaveTech/radiantwave-cpp.git?ref=dev";
     nixos-raspberrypi.url = "github:nvmd/nixos-raspberrypi/main";
   };
 
@@ -22,6 +22,35 @@
     }@inputs:
     let
       system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      # Plymouth theme: renders the RadiantWave SVG to a full-HD splash.png
+      # at build time (librsvg), so the theme is hermetic and resolution-
+      # independent. The .plymouth file's /usr paths are rewritten to $out
+      # (the NixOS module's initrd fixup rewrites store paths again).
+      radiantwavePlymouth = pkgs.stdenv.mkDerivation {
+        pname = "radiantwave-plymouth";
+        version = "1.0.0";
+
+        nativeBuildInputs = [ pkgs.librsvg ];
+
+        src = ./assets/RWT-Circular-Color-ForOnDark.svg;
+
+        buildPhase = ''
+          mkdir -p $out/share/plymouth/themes/radiantwave
+          rsvg-convert \
+            --keep-aspect-ratio \
+            --background-color=#111318 \
+            --width=3840 \
+            --height=2160 \
+            --output=$out/share/plymouth/themes/radiantwave/splash.png \
+            $src
+          sed 's,/usr/,'"$out"'/,g' ${./plymouth-theme/radiantwave.plymouth} \
+            > $out/share/plymouth/themes/radiantwave/radiantwave.plymouth
+          cp ${./plymouth-theme/radiantwave.script} \
+            $out/share/plymouth/themes/radiantwave/radiantwave.script
+        '';
+      };
 
       mkKioskSystem = { system, radiantwave, upgradeFlakeRef, extraModules ? [], diskModule, enableAutoUpgrade ? true, extraSpecialArgs ? {}}:
         nixpkgs.lib.nixosSystem {
@@ -30,6 +59,7 @@
           specialArgs = {
             inherit radiantwave;
             inherit upgradeFlakeRef;
+            inherit radiantwavePlymouth;
           } // extraSpecialArgs;
 
           modules = [
@@ -48,6 +78,7 @@
           specialArgs = {
             inherit radiantwave upgradeFlakeRef;
             inherit nixos-raspberrypi;
+            inherit radiantwavePlymouth;
           };
 
           modules = [