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>

tools/test-live-iso.sh

@@ -0,0 +1,49 @@
+#!/usr/bin/env bash
+# Build the Nomarchy live ISO and boot it in QEMU for a try-before-install
+# run. Ported from the previous Nomarchy iteration. See docs/TESTING.md
+# for what to verify once it's up.
+
+set -e
+cd "$(dirname "$0")/.."
+
+echo "Building Nomarchy live ISO..."
+nix build .#nixosConfigurations.nomarchy-live.config.system.build.isoImage
+
+ISO=$(ls -1 result/iso/*.iso 2>/dev/null | head -n 1)
+if [ -z "$ISO" ]; then
+    echo "Error: ISO build succeeded but no .iso file found in result/iso/" >&2
+    exit 1
+fi
+
+# Prefer UEFI with OVMF so the ISO boots the same way a modern install
+# does; fall back to legacy BIOS if OVMF isn't available on this host.
+OVMF_CANDIDATES=(
+    "/run/current-system/sw/share/OVMF/OVMF_CODE.fd"
+    "/run/current-system/sw/share/qemu/edk2-x86_64-code.fd"
+    "/nix/var/nix/profiles/system/sw/share/OVMF/OVMF_CODE.fd"
+    "/usr/share/OVMF/OVMF_CODE.fd"
+)
+BIOS_ARG=()
+for c in "${OVMF_CANDIDATES[@]}"; do
+    if [ -f "$c" ]; then
+        BIOS_ARG=(-drive "if=pflash,format=raw,readonly=on,file=$c")
+        VARS="${c%_CODE.fd}_VARS.fd"
+        [ -f "$VARS" ] && BIOS_ARG+=(-drive "if=pflash,format=raw,readonly=on,file=$VARS")
+        break
+    fi
+done
+
+# KVM if the host supports it; software emulation otherwise (slow).
+ACCEL_ARG=()
+[ -r /dev/kvm ] && ACCEL_ARG=(-enable-kvm -cpu host)
+
+echo "Launching ISO: $ISO"
+# virtio-vga-gl + gl=on gives the guest real OpenGL — Hyprland and
+# Ghostty need it; without GL the session may fail to start.
+exec qemu-system-x86_64 \
+    "${ACCEL_ARG[@]}" \
+    -m 4096 -smp 2 \
+    "${BIOS_ARG[@]}" \
+    -device virtio-vga-gl -display gtk,gl=on \
+    -device virtio-net-pci,netdev=n0 -netdev user,id=n0 \
+    -cdrom "$ISO" -boot d