Function execute 

pub async fn execute(
    request: RequestPayload,
    exec_ctx: Arc<ExecutionContext>,
) -> ExecutorResult<Either<ResponsePayload, BoxStream>>

Execute one stateful conversation turn.

Thin shim over ExecuteRequest for callers that don’t need per-request auth override.

Errors

Returns [ExecutorError] if rehydration or (non-streaming) LLM inference fails.