Overlap traversal against the FAT leaf AABBs — no tight body-AABB re-test and no filtering.
Used by persistent-pair discovery: a pair must exist whenever the two fat boxes could
bring the bodies into contact while both coast inside them, so the leaf test must be the
fat node AABB (already tested during descent), NOT the current tight body AABB.
Overlap traversal against the FAT leaf AABBs — no tight body-AABB re-test and no filtering. Used by persistent-pair discovery: a pair must exist whenever the two fat boxes could bring the bodies into contact while both coast inside them, so the leaf test must be the fat node AABB (already tested during descent), NOT the current tight body AABB.