Function simulate_intent_parallel 

pub async fn simulate_intent_parallel(
    catalog: &ContentCatalog,
    sim_config: &str,
    run: ParallelRun,
    resolver: &DynDataResolver<'_>,
    progress: &dyn ProgressSink,
) -> Result<Vec<u8>, ApplicationError>

Resolve sim_config once, run total_iters iterations across num_threads, encode the result.