Function invoke_agent 

pub async fn invoke_agent(
    agent: &str,
    model: &str,
    context: &str,
    message: &str,
) -> Result<InvokeResult>

Invoke an agent CLI one-shot and return structured result with token usage.

Delegates to runner::direct::run_direct() for command building, execution, parsing, and error classification.

Writes temp files to ~/.orch/state/control/{pid}/.