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/retro-82/btop.theme

@@ -0,0 +1,63 @@
+# Main background, empty for terminal default, need to be empty if you want transparent background
+theme[main_bg]=""
+
+# Main text color
+theme[main_fg]="#f6dcac"
+
+# Title color for boxes
+theme[title]="#3f8f8a"
+
+# Highlight color for keyboard shortcuts
+theme[hi_fg]="#8cbfb8"
+
+# Background color of selected item in processes box
+theme[selected_bg]="#134e5a"
+
+# Foreground color of selected item in processes box
+theme[selected_fg]="#f6dcac"
+
+# Color of inactive/disabled text
+theme[inactive_fg]="#134e5a"
+
+# Misc colors for processes box including mini cpu graphs, details memory graph and details status text
+theme[proc_misc]="#3f8f8a"
+
+# Box outline and divider line color
+theme[cpu_box]="#e97b3c"
+theme[mem_box]="#e97b3c"
+theme[net_box]="#e97b3c"
+theme[proc_box]="#e97b3c"
+theme[div_line]="#134e5a"
+
+# Gradient for all meters and graphs
+theme[temp_start]="#a7c9c6"
+theme[temp_mid]="#8cbfb8"
+theme[temp_end]="#028391"
+
+theme[cpu_start]="#a7c9c6"
+theme[cpu_mid]="#e97b3c"
+theme[cpu_end]="#f85525"
+
+theme[free_start]="#faa968"
+theme[free_mid]="#e97b3c"
+theme[free_end]="#f85525"
+
+theme[cached_start]="#faa968"
+theme[cached_mid]="#e97b3c"
+theme[cached_end]="#f85525"
+
+theme[available_start]="#faa968"
+theme[available_mid]="#e97b3c"
+theme[available_end]="#f85525"
+
+theme[used_start]="#faa968"
+theme[used_mid]="#e97b3c"
+theme[used_end]="#f85525"
+
+theme[download_start]="#faa968"
+theme[download_mid]="#e97b3c"
+theme[download_end]="#f85525"
+
+theme[upload_start]="#faa968"
+theme[upload_mid]="#e97b3c"
+theme[upload_end]="#f85525"