Implement physical inventory system per D-065:
- CarriedBy(StableId) component marks items as carried by an entity
- ItemName and InventorySlot components for display and slot assignment
- Take verb: removes TilePosition, adds CarriedBy + InventorySlot
- Place verb: removes CarriedBy + InventorySlot, adds TilePosition
- Observer snapshot populates player_inventory from carried items query
- Info boundary: carried items lack TilePosition, naturally excluded
from all spatial queries (visibility, interactions) for other entities
- 9-slot capacity (3x3 grid per OQ-24), auto-assigns first free slot
- 8 new tests covering take, place, sequential slots, full rejection
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>