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-wsl.nix

@@ -0,0 +1,53 @@
+# ============================================================================
+# Windows Subsystem for Linux (WSL) Configuration
+# ============================================================================
+# Configuration for NixOS running in WSL2 on Windows.
+# Integrates with nixos-wsl for WSL-specific functionality.
+
+{
+  lib,
+  config,
+  inputs,
+  ...
+}:
+{
+  imports = [
+    inputs.nixos-wsl.nixosModules.default
+    inputs.vscode-server.nixosModules.default
+  ];
+
+  # ========== Options ==========
+  options.athenix.host.wsl.user = lib.mkOption {
+    type = lib.types.str;
+    default = "engr-ugaif";
+    description = "The default user to log in as in WSL.";
+  };
+
+  config = {
+    # ========== WSL Configuration ==========
+    wsl.enable = true;
+    # Use forUser if set, otherwise fall back to wsl.user option
+    wsl.defaultUser =
+      if config.athenix.forUser != null then config.athenix.forUser else config.athenix.host.wsl.user;
+
+    # ========== Software Profile ==========
+    athenix.sw.enable = lib.mkDefault true;
+    athenix.sw.type = lib.mkDefault "headless";
+
+    # ========== Remote Development ==========
+    services.vscode-server.enable = true;
+
+    # ========== Disable Irrelevant Systems ==========
+    # WSL doesn't use traditional boot or disk management
+    disko.enableConfig = lib.mkForce false;
+    boot.loader.systemd-boot.enable = lib.mkForce false;
+    boot.loader.grub.enable = lib.mkForce false;
+
+    # WSL manages its own networking
+    systemd.network.enable = lib.mkForce false;
+
+    # Provide dummy values for required options from boot.nix
+    athenix.host.filesystem.device = "/dev/null";
+    athenix.host.filesystem.swapSize = "0G";
+  };
+}