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.