Function execute_deployment_pack 

pub async fn execute_deployment_pack(
    config: &DeployerConfig,
    plan: &PlanContext,
    dispatch: &DeploymentDispatch,
) -> Result<Option<ExecutionOutcome>>

Executes the resolved deployment pack via a registered executor.

Returns Ok(true) when an executor was registered and ran, Ok(false) when no executor is available yet, and Err on fatal failures.