refactor: create glue/ and variants/ directories

- Add glue/ for fleet generation logic and common configuration
- Add variants/ for hardware type modules
- Improves separation of concerns and module organization

variants/nix-ephemeral.nix

@@ -0,0 +1,67 @@
+# ============================================================================
+# Ephemeral/Diskless System Configuration
+# ============================================================================
+# Configuration for systems that run entirely from RAM without persistent storage.
+# Suitable for kiosks, netboot clients, and stateless workstations.
+# All data is lost on reboot.
+
+{ inputs, ... }:
+{
+  config,
+  lib,
+  modulesPath,
+  ...
+}:
+{
+  imports = [
+    (modulesPath + "/installer/scan/not-detected.nix")
+  ];
+
+  # ========== Boot Configuration ==========
+  boot.initrd.availableKernelModules = [
+    "xhci_pci" # USB 3.0 support
+    "nvme" # NVMe support
+    "usb_storage" # USB storage devices
+    "sd_mod" # SD card support
+    "sdhci_pci" # SD card host controller
+  ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ "kvm-intel" ]; # Intel virtualization support
+  boot.extraModulePackages = [ ];
+  boot.kernelParams = [
+    "quiet" # Minimal boot messages
+    "splash" # Show Plymouth boot splash
+    "boot.shell_on_fail" # Emergency shell on boot failure
+    "udev.log_priority=3" # Reduce udev logging
+    "rd.systemd.show_status=auto" # Show systemd status during boot
+  ];
+
+  # ========== Ephemeral Configuration ==========
+  # No persistent storage - everything runs from RAM
+  athenix.host.filesystem.swapSize = lib.mkForce "0G";
+  athenix.host.filesystem.device = lib.mkForce "/dev/null"; # Dummy device
+  athenix.host.buildMethods = lib.mkDefault [
+    "iso" # Live ISO image
+    "ipxe" # Network boot
+  ];
+
+  # Disable disk management for RAM-only systems
+  disko.enableConfig = lib.mkForce false;
+
+  # Define tmpfs root filesystem
+  fileSystems."/" = {
+    device = "none";
+    fsType = "tmpfs";
+    options = [
+      "defaults"
+      "size=50%"
+      "mode=755"
+    ];
+  };
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+
+  athenix.sw.enable = lib.mkDefault true;
+  athenix.sw.type = lib.mkDefault "stateless-kiosk";
+}