s&box Inventory System: PlayerInventory with Auto-Switch and Ammo Consolidation

Managing player inventory in s&box requires handling weapon slots, ammo, pickup/drop mechanics, and auto-switching logic. Common implementation challenges include:

1. Replicated inventory state across network
2. Weapon slot management and swapping
3. Ammo consolidation when picking up same weapon type
4. Proper cleanup when dropping weapons
5. Auto-switching logic based on weapon value