Values.SendMessageEventsSourceEvent stream for chat message responses using the content block model. Events follow a lifecycle: responseCreated -> responseInProgress -> (contentBlockStart/contentBlockDelta/contentBlockStop events) -> responseCompleted|responseFailed SendMessage always uses content block mode — legacy per-field events (outputTextDelta, functionCallArgumentsDelta, etc.) are not emitted.
type nonrec t = {responseCreated : SendMessageResponseCreatedEvent.t option;Emitted when the response is created
*)responseInProgress : SendMessageResponseInProgressEvent.t option;Emitted while the response is being generated
*)responseCompleted : SendMessageResponseCompletedEvent.t option;Emitted when the response completes successfully
*)responseFailed : SendMessageResponseFailedEvent.t option;Emitted when the response fails
*)summary : SendMessageSummaryEvent.t option;Emitted to provide a summary of agent actions
*)heartbeat : SendMessageHeartbeatEvent.t option;Heartbeat event sent periodically to keep the connection alive during idle periods
*)contentBlockStart : SendMessageContentBlockStartEvent.t option;Emitted when a new content block starts
*)contentBlockDelta : SendMessageContentBlockDeltaEvent.t option;Emitted for each incremental content delta within a content block
*)contentBlockStop : SendMessageContentBlockStopEvent.t option;Emitted when a content block is complete
*)}