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>

themes/catppuccin-latte.json

@@ -0,0 +1,39 @@
+{
+  "version": 1,
+  "name": "Catppuccin Latte",
+  "slug": "catppuccin-latte",
+  "mode": "light",
+  "wallpaper": "",
+  "colors": {
+    "base": "#eff1f5",
+    "mantle": "#cbcdd0",
+    "surface": "#bcc0cc",
+    "overlay": "#acb0be",
+    "text": "#4c4f69",
+    "subtext": "#5c5f77",
+    "muted": "#acb0be",
+    "accent": "#1e66f5",
+    "accentAlt": "#ea76cb",
+    "good": "#40a02b",
+    "warn": "#df8e1d",
+    "bad": "#d20f39"
+  },
+  "ansi": [
+    "#bcc0cc",
+    "#d20f39",
+    "#40a02b",
+    "#df8e1d",
+    "#1e66f5",
+    "#ea76cb",
+    "#179299",
+    "#5c5f77",
+    "#acb0be",
+    "#d20f39",
+    "#40a02b",
+    "#df8e1d",
+    "#1e66f5",
+    "#ea76cb",
+    "#179299",
+    "#6c6f85"
+  ]
+}