refactor: reorganize directory structure (variants -> hw, glue -> fleet)

- Rename variants/ to hw/ for clearer hardware module naming
- Rename glue/ to fleet/ for more intuitive fleet management
- Move boot/fs configuration from glue/boot.nix to separate fleet/boot.nix and fleet/fs.nix
- Improve separation of concerns between boot, filesystem, and common config

hw/nix-surface.nix

@@ -0,0 +1,57 @@
+# ============================================================================
+# Microsoft Surface Tablet Configuration
+# ============================================================================
+# Hardware configuration for Surface Go tablets in kiosk mode.
+# Uses nixos-hardware module and older kernel for Surface-specific drivers.
+
+{
+  config,
+  lib,
+  modulesPath,
+  inputs,
+  ...
+}:
+{
+  imports = [
+    (modulesPath + "/installer/scan/not-detected.nix")
+    inputs.nixos-hardware.nixosModules.microsoft-surface-go
+  ];
+
+  # ========== Boot Configuration ==========
+
+  boot.initrd.availableKernelModules = [
+    "xhci_pci" # USB 3.0 support
+    "nvme" # NVMe support (though Surface uses eMMC)
+    "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
+    "intel_ipu3_imgu" # Intel camera image processing
+    "intel_ipu3_isys" # Intel camera sensor interface
+    "fbcon=map:1" # Framebuffer console mapping
+    "i915.enable_psr=0" # Disable Panel Self Refresh (breaks resume)
+    "i915.enable_dc=0" # Disable display power saving
+  ];
+
+  # ========== Filesystem Configuration ==========
+  athenix.host.filesystem.swapSize = lib.mkDefault "8G";
+  athenix.host.filesystem.device = lib.mkDefault "/dev/mmcblk0"; # eMMC storage # eMMC storage
+  athenix.host.buildMethods = lib.mkDefault [ "installer-iso" ];
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+
+  # ========== Hardware Configuration ==========
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault config.hardware.enableRedistributableFirmware;
+
+  # ========== Software Profile ==========
+  athenix.sw.enable = lib.mkDefault true;
+  athenix.sw.type = lib.mkDefault "tablet-kiosk"; # Touch-optimized kiosk mode
+}