Rebuild now runs once per frame via ExecuteAlways Update (OnValidate only sets a dirty flag + QueuePlayerLoopUpdate), fixing inspector drag stutter from stacked delayCalls. Adds automatic BoxCollider generation (4 frame bars, opening slab, optional pedestal box for raised pictures) with an ownership list so manual colliders stay untouched. Corner radius is intentionally ignored for colliders. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>