deliver

Push swatch directly into incoming, applying the configured DeliveryPolicy.

Throws IllegalStateException once the seam is SeamState.Torn — a real seam completes incoming on tear and never delivers again, so this fake rejects post-tear delivery rather than silently masking a frame that could never arrive.

Push a frame from from into incoming, stamping sender and a monotonically increasing sequence (receiver-local, starting at 1).