Install omarchy-installer + omarchy-settings into the live ISO

Two motivations:

1. Plymouth: the omarchy plymouth theme + /etc/plymouth/plymouthd.conf
   ship from omarchy-settings (theme at /usr/share/plymouth/themes/omarchy,
   plymouthd.conf via the package's post_install etc-overrides hook).
   Without omarchy-settings on the live ISO, mkarchiso builds the initrd
   with plymouth pointing at the default theme instead of Omarchy's. Now
   it picks up the Omarchy theme on boot like the installed system does.

2. Drops the .pkg.tar.zst extraction hack in .automated_script.sh:
   OMARCHY_PATH=/usr/share/omarchy is the real package install path, so
   use_omarchy_helpers no longer needs to bsdtar pieces out of the
   offline mirror into /tmp/omarchy-iso.

configs/airootfs/root/.automated_script.sh

@@ -2,25 +2,10 @@
 set -euo pipefail
 
 use_omarchy_helpers() {
-  # Neither omarchy-installer nor omarchy-settings is installed in the live
-  # ISO; we just have the .pkg.tar.zst files in the offline mirror. Extract
-  # the bits we need (install/ from the installer; logo.txt/icon.txt and
-  # default/ from settings) to /tmp/omarchy-iso so OMARCHY_PATH resolves to
-  # a tree that looks like a real install.
+  # omarchy-installer + omarchy-settings are installed into the live ISO (see
+  # build-iso.sh arch_packages), so /usr/share/omarchy is the real tree.
   export OMARCHY_MIRROR="$(cat /root/omarchy_mirror)"
-  if [[ ! -d /tmp/omarchy-iso ]]; then
-    local installer_pkg settings_pkg
-    installer_pkg=$(ls /var/cache/omarchy/mirror/offline/omarchy-installer-*.pkg.tar.zst 2>/dev/null | head -1)
-    settings_pkg=$(ls /var/cache/omarchy/mirror/offline/omarchy-settings-*.pkg.tar.zst 2>/dev/null | head -1)
-    [[ -n $installer_pkg && -n $settings_pkg ]] || {
-      echo "ERROR: omarchy-installer or omarchy-settings missing from offline mirror" >&2
-      exit 1
-    }
-    mkdir -p /tmp/omarchy-iso
-    bsdtar -xf "$installer_pkg" -C /tmp/omarchy-iso usr/share/omarchy
-    bsdtar -xf "$settings_pkg"  -C /tmp/omarchy-iso usr/share/omarchy
-  fi
-  export OMARCHY_PATH=/tmp/omarchy-iso/usr/share/omarchy
+  export OMARCHY_PATH=/usr/share/omarchy
   export OMARCHY_INSTALL=$OMARCHY_PATH/install
   export OMARCHY_INSTALL_LOG_FILE=/var/log/omarchy-install.log
   source "$OMARCHY_INSTALL/helpers/all.sh"