The initrd was missing virtio drivers, preventing the root
filesystem from being detected during boot.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The OpenStack image labels the root partition "nixos", so use
/dev/disk/by-label/nixos instead of /dev/vda1.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>