SpringBone: applyVelocityCorrection keeps push-out-manufactured outward velocity — joints coast 4-8cm after hard contact

**Problem**
applyVelocityCorrection() zeroes only inward normal velocity (if vn < 0.0), so the outward Verlet velocity that a collision push-out manufactures survives the next substep. The joint coasts outward for multiple frames.

**Observed drift**
During segment-collision testing (Task 4), hard contact against hand-held objects or cloth folds created 4-8cm fixture drift in waist-length chains — joints drifting visibly away from the contact surface for 0.1–0.2s after push-out.

**Pre-existing, affects every collider**
This is not introduced by fitClothCollisionToMesh — it's a general issue with how Verlet velocity is handled post-collision. Discovered incidentally while testing segment collision; applies to sphere, capsule, and plane colliders today.

**Reference**
Related to #381 cloth-collision fidelity; discovered during validation gate 6.3 (oracle measurement) and gate 6.4 (visual inspection).

Start by locating applyVelocityCorrection() in the SpringBone collision code and trace how Verlet velocity is updated after push-out for sphere, capsule, and plane colliders. Reproduce the segment-collision scenario from Task 4, using validation gates 6.3 and 6.4 as references; done means hard contacts no longer leave joints coasting outward for multiple frames.

Written by the indexing model from the issue text.