Guard MASK_SIEGE and regular mob MASK_PET scans were dead code: no mob
ever carries either mask. Removed so they cannot start auto-aggroing
siege engines if the masks are wired up later. Safehold guards no
longer aggro siege engines. Guards still respond to a siege engine
damaging a city building.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>