Add Steam Deck (nix-deck) configuration with Jovian-NixOS and remote building

- Add Jovian-NixOS integration for Steam Deck hardware support
- Create nix-deck machine configuration with SteamOS role
- Add jovian-compat.nix for NixOS 25.05 compatibility (remove in 25.11+)
- Create remote-build role for distributed builds
- Configure zix790prors as build host
- Configure nix-book and nix-deck to use remote builder with fallback
- Add comprehensive setup documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

machines/nix-deck/configuration.nix

@@ -0,0 +1,41 @@
+{ pkgs, ... }:
+{
+  imports = [
+    ./hardware-configuration.nix
+  ];
+
+  roles = {
+    audio.enable = true;
+    bluetooth.enable = true;
+    desktop = {
+      enable = true;
+      wayland = true;
+      gaming.enable = true;
+      kde = true;
+      sddm = true;
+      steamos = {
+        enable = true;
+        autoStart = false;
+        desktopSession = "plasmawayland";
+      };
+    };
+    remote-build.builders = [{
+      hostName = "zix790prors";
+      maxJobs = 16;
+      speedFactor = 4;  # Prefer remote heavily on Steam Deck
+    }];
+    users = {
+      enable = true;
+      extraGroups = [ "video" ];
+    };
+  };
+
+  # Bootloader
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+
+  networking.hostName = "nix-deck";
+  networking.networkmanager.enable = true;
+
+  system.stateVersion = "25.05";
+}