call_participant_removed· reason_code· applies to service_callA participant whose `(actor_id, device_id)` has an effective kick in `call_moderation`, or whose actor has an effective ban there, attempted to re-establish a media leg or re-issue a join token. Token issuer / SFU MUST refuse; a banned actor MUST NOT rejoin until the ban is lifted. See zh/crypto-media/webrtc-signaling.md §3a.