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/kanagawa.json

@@ -0,0 +1,39 @@
+{
+  "version": 1,
+  "name": "Kanagawa",
+  "slug": "kanagawa",
+  "mode": "dark",
+  "wallpaper": "",
+  "colors": {
+    "base": "#1f1f28",
+    "mantle": "#1a1a22",
+    "surface": "#090618",
+    "overlay": "#727169",
+    "text": "#dcd7ba",
+    "subtext": "#c8c093",
+    "muted": "#727169",
+    "accent": "#7e9cd8",
+    "accentAlt": "#957fb8",
+    "good": "#76946a",
+    "warn": "#c0a36e",
+    "bad": "#c34043"
+  },
+  "ansi": [
+    "#090618",
+    "#c34043",
+    "#76946a",
+    "#c0a36e",
+    "#7e9cd8",
+    "#957fb8",
+    "#6a9589",
+    "#c8c093",
+    "#727169",
+    "#e82424",
+    "#98bb6c",
+    "#e6c384",
+    "#7fb4ca",
+    "#938aa9",
+    "#7aa89f",
+    "#dcd7ba"
+  ]
+}