test(tlbo,umda,simulated_annealing,tabu_search,tpe,snes,rvea,spea2): pin comparison and geometry helpers

Phase 1 tests for eight more algorithms — the feasibility-first
comparison helpers (better / better_than / compare_so / worse_than),
plus algorithm-specific pure functions:
- tlbo: best_index min/max/tie.
- tpe: oriented_target sign-flip + penalty; split_good_bad partition
  and clamp-to-at-least-one-each.
- snes: nes_utilities sum-to-zero + descending + positive-best.
- rvea: unit_normalize (3-4-5 → 0.6/0.8), zero-vector passthrough;
  closest_reference smallest-angle; smallest_neighbor_angle = π/2 for
  orthogonal refs.
- spea2: euclidean distance basics; binary_tournament prefers lower
  fitness.

src/algorithms/umda.rs

@@ -449,4 +449,30 @@ mod tests {
         });
         let _ = opt.run(&DummyMo);
     }
+
+    // ---- Mutation-test pinned helpers --------------------------------------
+
+    #[test]
+    fn compare_so_feasibility_first_and_direction() {
+        let feasible = Evaluation::new(vec![100.0]);
+        let infeasible = Evaluation::constrained(vec![0.0], 1.0);
+        assert_eq!(compare_so(&feasible, &infeasible, Direction::Minimize), std::cmp::Ordering::Less);
+        let lo = Evaluation::new(vec![1.0]);
+        let hi = Evaluation::new(vec![2.0]);
+        assert_eq!(compare_so(&lo, &hi, Direction::Minimize), std::cmp::Ordering::Less);
+        assert_eq!(compare_so(&lo, &hi, Direction::Maximize), std::cmp::Ordering::Greater);
+        let v_lo = Evaluation::constrained(vec![0.0], 0.2);
+        let v_hi = Evaluation::constrained(vec![0.0], 0.8);
+        assert_eq!(compare_so(&v_lo, &v_hi, Direction::Minimize), std::cmp::Ordering::Less);
+    }
+
+    #[test]
+    fn better_than_so_is_strict_less() {
+        let lo = Evaluation::new(vec![1.0]);
+        let hi = Evaluation::new(vec![2.0]);
+        assert!(better_than_so(&lo, &hi, Direction::Minimize));
+        assert!(!better_than_so(&hi, &lo, Direction::Minimize));
+        let eq = Evaluation::new(vec![1.0]);
+        assert!(!better_than_so(&lo, &eq, Direction::Minimize));
+    }
 }