One end user's conversations for the calling API-key client, most recently active first.
Scoped to the calling API-key CLIENT (any of its keys — a rotated key reads what its predecessor wrote) and to the one endUserRef named, which is required. Only runs started through the /v1 run routes after this surface shipped carry a client, so earlier runs are not returned. A run another client started under the same conversationId is never included.