Function concurrent 

pub async fn concurrent(
    registry: &AgentRegistry,
    input: &str,
    agents: &[ConcurrentAgentRef],
    aggregation_config: &AggregationConfig,
    llm: Option<&dyn LLMProvider>,
    min_required: Option<usize>,
    timeout_ms: Option<u64>,
    on_partial_failure: PartialFailureAction,
    vote_parallelism: Option<usize>,
) -> Result<ConcurrentResult>

Run multiple agents in parallel and aggregate results. The explicit arguments preserve the public orchestration call contract and its independent controls. The complete immutable root-gate ancestry is captured before spawning so every child preserves cycle detection.