Responses continuation lifecycle suppression

Chose suppressing every follow-up Responses lifecycle/terminal event and replayed principal-stream content over faithful passthrough because the principal already initialized and emitted its stream. A continuation may expose only its authoritative new answer through gateway-owned sequencing; forwarding its response.created, response.in_progress, terminal, or replayed principal items duplicates output and breaks terminal output_index identity. The gateway rebuilds one authoritative terminal.