Overhaul preseed.cfg from a semi-interactive installer (prompting for
LUKS passphrase and user credentials) to a fully unattended dev/test
setup with hardcoded credentials. Enable networking and configure a
Debian sid pin to pull Hyprland, UWSM, SDDM, and foot during
late_command. Add serial console support in GRUB for headless debugging.
Also update the FSD with the "match upstream Omarchy" design principle
and bump the last-updated date.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>