find potentially colliding body pairs, updates world.pairs.collidingPairs.
moved-only persistent-pair broadphase: a persistent pair set is populated by fat-AABB queries from
bodies that moved (escaped their fat leaf) or were added, then swept every frame. the emitted pairs
array is semantically identical to the old per-active-body scan (same pair set each frame;
intra-pair/record order may differ).
find potentially colliding body pairs, updates world.pairs.collidingPairs.
moved-only persistent-pair broadphase: a persistent pair set is populated by fat-AABB queries from bodies that moved (escaped their fat leaf) or were added, then swept every frame. the emitted pairs array is semantically identical to the old per-active-body scan (same pair set each frame; intra-pair/record order may differ).