Moves the NPC spawn / object placer audit + ground-snap
handlers out of main.cpp:
--snap-zone-to-ground --snap-project-to-ground
--audit-zone-spawns --audit-project-spawns
--list-zone-spawns --list-project-spawns
--diff-zone-spawns --info-spawn
All operate on creatures.json + objects.json sidecars and
the WHM terrain heightfield via WoweeTerrainLoader.
main.cpp drops 14,628 → 13,887 lines (-741). Behavior verified
by re-running --audit-zone-spawns on a test zone (PASSED with
0 issues, same as before).
