Cold-storage source for phase 3b (evict-to-disk): returns the meshes of
every cache chunk intersecting the given world AABB. The Scene filters the
result down to one bucket's members (by expressId + bucket base key), so
over-fetching neighbours is fine — providers should cache recently decoded
chunks since adjacent buckets restore together during a gesture.
Cold-storage source for phase 3b (evict-to-disk): returns the meshes of every cache chunk intersecting the given world AABB. The Scene filters the result down to one bucket's members (by expressId + bucket base key), so over-fetching neighbours is fine — providers should cache recently decoded chunks since adjacent buckets restore together during a gesture.