message: Offset NPC IDs by 1 to avoid ID 0
diff: #include "NPCManager.hpp"
  // these are added to the NPC's static key to avoid collisions
  -const int NPC_ID_OFFSET = 0;
  +const int NPC_ID_OFFSET = 1;
  const int MOB_ID_OFFSET = 10000;
  const int MOB_GROUP_ID_OFFSET = 20000;
  