tsp_operators_compare.rs runs NSGA-II four times on the KroAB-25 bi-objective TSP, holding everything constant except the crossover operator. Ranks OX, PMX, CX, ERX by hypervolume against a fixed reference point, plus front size, unique-point count, and runtime. Pedagogical demonstration that the right comparison metric for a Pareto search is hypervolume, not single-objective fitness.