TilePosition component with discrete grid coordinates, flat-storage WalkabilityMap resource with O(1) can_move_to() lookup, MoveIntent component and validate_movement system. Movement validated against walkability map each tick, blocking all NPC and player movement through unwalkable tiles. 11 unit tests + 1 integration test. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>