Function run_scenarios 

fn run_scenarios(
    scenarios: &[(&Model<'_, '_>, &Prepared)],
    settings: &SimulationSettings,
    full: bool,
) -> Result<(Vec<Tally>, Vec<bool>), PricingError>

Runs every scenario on the same paths. Scenarios that share their dynamics share each path’s trajectory: it is stepped once per path per dynamics, and read under each scenario’s market. Returns the tallies and, per scenario, whether its trajectory was its own rather than the first scenario’s.