Refactor server entity update flow to process entities individually,
skipping those whose chunk is not loaded. System update methods now
accept a single entity instead of iterating the full registry view,
and `ServerWorld::get_chunk_ref_count` is added to determine if an
entity's chunk is active.
Move direction into the transform component and include it in server-to-client entity updates. Client now sets transform direction from the network message and uses it to compute yaw for model rotation, so entities visually face their movement direction. Refactor net_utils to support arbitrary Vec3 fields.
Add movement constants for pigs and switch deceleration to per-axis friction so creatures stop naturally. Extend wander boost duration for smoother behavior.
Preserve sign when clamping velocity; negative velocities now clamp to zero instead of flipping direction. Support loading hitbox definitions from JSON arrays and objects. Tune pig entity movement, spawn height, and wander probabilities.
Add AIBase and WanderAITag components, a WanderAISystem, and a MoveBoost component to control wandering behavior. Replace the old MoveState with MoveBoost and include a horizontal random direction helper.
