SMSG_GOSSIP_MESSAGE (3.3.5a) improvements:
- Validate 20-byte minimum for npcGuid + menuId + titleTextId + optionCount
- Cap optionCount to 64 (prevents unbounded memory allocation)
- Validate 12-byte minimum before each option read (fixed fields + 2 strings)
- Cap questCount to 64 (prevents unbounded memory allocation)
- Validate 18-byte minimum before each quest read (fixed fields + title string)
- Graceful truncation with partial list support
Prevents DoS from servers sending malformed gossip menus with huge option/quest lists.