feat: Nomarchy ground-up rewrite on NixOS 26.05

Full replacement of the previous iteration, rebuilt around three ideas:

- Pure evaluation: theme-state.json lives inside the flake and is read
  via the nomarchy.stateFile option — no --impure, ever.
- All-Home-Manager theming: `nomarchy-theme-sync apply` writes the JSON
  and runs `home-manager switch`; every theme change is one atomic,
  rollbackable generation. Wallpaper (swww) is the sole runtime piece.
- Flat, downstream-first layout: modules/{nixos,home} with one
  options.nix each, exported as nixosModules/homeModules + overlay +
  flake template; system (nixos-rebuild) and desktop (home-manager
  switch) rebuild paths are fully split.

Ships 21 themes imported from the previous iteration (palettes,
wallpapers, btop themes, six whole-swap Waybar identities), Stylix for
the GTK/Qt/cursor long tail, a live ISO target with offline theme
switching, and docs/TESTING.md with the QEMU verification workflow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

templates/downstream/README.md

@@ -0,0 +1,22 @@
+# My Nomarchy machine
+
+1. `nixos-generate-config --show-hardware-config > hardware-configuration.nix`
+2. Edit `flake.nix` (Nomarchy repo URL, username), `system.nix` (hostname,
+   user), `home.nix` (your packages).
+3. `git init && git add -A` — flakes only see tracked files, including
+   `theme-state.json`.
+4. System: `sudo nixos-rebuild switch --flake .#default`
+5. Desktop: `nix run home-manager -- switch --flake .#me`
+   (afterwards just `home-manager switch --flake .#me` — it's installed)
+6. Clone/symlink this directory to `~/.nomarchy` (or export
+   `NOMARCHY_PATH`) so `nomarchy-theme-sync` knows where the state lives.
+
+Day-to-day:
+
+```sh
+nomarchy-theme-sync list             # 21 shipped presets
+nomarchy-theme-sync apply gruvbox    # writes state + home-manager switch
+nomarchy-theme-sync bg next          # cycle wallpapers (instant, no rebuild)
+```
+
+The system layer only needs `nixos-rebuild` when you change `system.nix`.

templates/downstream/flake.nix

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+{
+  description = "My Nomarchy machine";
+
+  inputs = {
+    # Pin Nomarchy; nixpkgs and home-manager follow whatever it ships.
+    nomarchy.url = "github:YOUR-USER/nomarchy"; # <- point at the distro repo
+    nixpkgs.follows = "nomarchy/nixpkgs";
+    home-manager.follows = "nomarchy/home-manager";
+  };
+
+  outputs = { self, nomarchy, nixpkgs, home-manager, ... }:
+    let
+      system = "x86_64-linux";
+      username = "me"; # <- your login name
+
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [ nomarchy.overlays.default ];
+      };
+    in
+    {
+      # System layer — rebuilt rarely:
+      #   sudo nixos-rebuild switch --flake .#default
+      nixosConfigurations.default = nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = [
+          nomarchy.nixosModules.nomarchy   # the distro
+          ./hardware-configuration.nix     # from `nixos-generate-config`
+          ./system.nix                     # your machine
+        ];
+      };
+
+      # Desktop layer — rebuilt on every theme change, no sudo:
+      #   home-manager switch --flake .#me
+      # (`nomarchy-theme-sync apply <theme>` runs this for you.)
+      homeConfigurations.${username} = home-manager.lib.homeManagerConfiguration {
+        inherit pkgs;
+        modules = [
+          nomarchy.homeModules.nomarchy
+          ./home.nix
+          {
+            # Your theme state — written by nomarchy-theme-sync, baked
+            # in on every switch. Keep it git-tracked.
+            nomarchy.stateFile = ./theme-state.json;
+            home = {
+              inherit username;
+              homeDirectory = "/home/${username}";
+            };
+          }
+        ];
+      };
+    };
+}

templates/downstream/home.nix

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+# Your user environment. The Nomarchy desktop (Hyprland, Waybar,
+# Ghostty, theming engine, Stylix) comes from homeModules.nomarchy;
+# tune it via the nomarchy.* options, add your own packages and
+# programs below.
+{ pkgs, ... }:
+
+{
+  # Examples:
+  # nomarchy.terminal = "kitty";        # swap the default terminal
+  # nomarchy.waybar.enable = false;     # bring your own bar
+  # nomarchy.stylix.enable = false;     # opt out of GTK/Qt theming
+
+  home.packages = with pkgs; [
+    # firefox
+  ];
+}

templates/downstream/system.nix

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+# Your machine: bootloader, hostname, users, services.
+# The distro itself comes from nomarchy.nixosModules.nomarchy — override
+# any of its defaults here with plain NixOS options (they use mkDefault),
+# or via the nomarchy.system.* toggles.
+{ pkgs, ... }:
+
+{
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+
+  networking.hostName = "my-nomarchy";
+  time.timeZone = "UTC";
+  i18n.defaultLocale = "en_US.UTF-8";
+
+  users.users.me = { # <- keep in sync with `username` in flake.nix
+    isNormalUser = true;
+    extraGroups = [ "wheel" "networkmanager" "video" "input" ];
+  };
+
+  # Examples:
+  # nomarchy.system.greeter.enable = false;   # bring your own login manager
+  # environment.systemPackages = [ pkgs.htop ];
+
+  system.stateVersion = "26.05";
+}

templates/downstream/theme-state.json

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+{
+  "version": 1,
+  "name": "Tokyo Night",
+  "slug": "tokyo-night",
+  "mode": "dark",
+  "wallpaper": "",
+  "colors": {
+    "base": "#1a1b26",
+    "mantle": "#161720",
+    "surface": "#32344a",
+    "overlay": "#444b6a",
+    "text": "#a9b1d6",
+    "subtext": "#787c99",
+    "muted": "#444b6a",
+    "accent": "#7aa2f7",
+    "accentAlt": "#ad8ee6",
+    "good": "#9ece6a",
+    "warn": "#e0af68",
+    "bad": "#f7768e"
+  },
+  "ansi": [
+    "#32344a",
+    "#f7768e",
+    "#9ece6a",
+    "#e0af68",
+    "#7aa2f7",
+    "#ad8ee6",
+    "#449dab",
+    "#787c99",
+    "#444b6a",
+    "#ff7a93",
+    "#b9f27c",
+    "#ff9e64",
+    "#7da6ff",
+    "#bb9af7",
+    "#0db9d7",
+    "#acb0d0"
+  ],
+  "fonts": {
+    "mono": "JetBrainsMono Nerd Font",
+    "ui": "Inter",
+    "size": 11
+  },
+  "ui": {
+    "gapsIn": 5,
+    "gapsOut": 12,
+    "borderSize": 2,
+    "rounding": 10,
+    "activeOpacity": 1.0,
+    "inactiveOpacity": 0.95,
+    "terminalOpacity": 0.96,
+    "blur": true,
+    "shadow": true
+  }
+}