Function convex_rollout_objective 

pub fn convex_rollout_objective(
    rollout: &ConvexContactRollout<'_>,
    objective: &FinalStateObjective<'_>,
) -> f64

Run the nominal rollout and return the objective only — the FD oracle for gates, and a cheap primal probe. The dynamics are identical to convex_adjoint_gradient’s forward pass (and to Simulator::step_with_contacts).