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/summer-day/btop.theme

@@ -0,0 +1,86 @@
+# Main background, empty for terminal default, need to be empty if you want transparent background
+theme[main_bg]="#fdf6e3"
+
+# Main text color
+theme[main_fg]="#5c6a72"
+
+# Title color for boxes
+theme[title]="#5c6a72"
+
+# Highlight color for keyboard shortcuts
+theme[hi_fg]="#f85552"
+
+# Background color of selected items
+theme[selected_bg]="#e6e2cc"
+
+# Foreground color of selected items
+theme[selected_fg]="#dfa000"
+
+# Color of inactive/disabled text
+theme[inactive_fg]="#bdc3af"
+
+# Color of text appearing on top of graphs, i.e uptime and current network graph scaling
+theme[graph_text]="#5c6a72"
+
+# Misc colors for processes box including mini cpu graphs, details memory graph and details status text
+theme[proc_misc]="#8da101"
+
+# Cpu box outline color
+theme[cpu_box]="#bdc3af"
+
+# Memory/disks box outline color
+theme[mem_box]="#bdc3af"
+
+# Net up/down box outline color
+theme[net_box]="#bdc3af"
+
+# Processes box outline color
+theme[proc_box]="#bdc3af"
+
+# Box divider line and small boxes line color
+theme[div_line]="#bdc3af"
+
+# Temperature graph colors
+theme[temp_start]="#8da101"
+theme[temp_mid]="#dfa000"
+theme[temp_end]="#f85552"
+
+# CPU graph colors
+theme[cpu_start]="#8da101"
+theme[cpu_mid]="#dfa000"
+theme[cpu_end]="#f85552"
+
+# Mem/Disk free meter
+theme[free_start]="#f85552"
+theme[free_mid]="#dfa000"
+theme[free_end]="#8da101"
+
+# Mem/Disk cached meter
+theme[cached_start]="#3a94c5"
+theme[cached_mid]="#35a77c"
+theme[cached_end]="#8da101"
+
+# Mem/Disk available meter
+theme[available_start]="#f85552"
+theme[available_mid]="#dfa000"
+theme[available_end]="#8da101"
+
+# Mem/Disk used meter
+theme[used_start]="#8da101"
+theme[used_mid]="#dfa000"
+theme[used_end]="#f85552"
+
+# Download graph colors
+theme[download_start]="#8da101"
+theme[download_mid]="#35a77c"
+theme[download_end]="#3a94c5"
+
+# Upload graph colors
+theme[upload_start]="#dfa000"
+theme[upload_mid]="#df69ba"
+theme[upload_end]="#f85552"
+
+# Process box color gradient for threads, mem and cpu usage
+theme[process_start]="#8da101"
+theme[process_mid]="#f85552"
+theme[process_end]="#f85552"