Function find_optimal 

pub fn find_optimal(
    workload: &WorkloadConfig,
    pool: &PoolConfig,
    dist: &LatencyDistribution,
    opts: &SimulationOptions,
) -> Result<OptimalResult, PoolsimError>

Finds the smallest pool size that satisfies target constraints.

Falls back to pool.max_pool_size when no candidate satisfies both utilization and p99 wait targets.

Errors

Returns propagated distribution/simulation/queue-model errors.