docs(book): permutation toolkit and multi-objective combinatorial cookbook

- Rewrites cookbook/permutation.md to cover the new operator toolkit:
  initializers, crossovers (OX/PMX/CX/ERX), mutations, a 'what should I
  use' picker, and a worked GA-on-TSP example. JSS multiset section
  explains why the strict-permutation crossovers don't compose with
  operation-string encodings and shows the local POX pattern.

- Adds cookbook/multi-objective-combinatorial.md: bi-objective TSP via
  NSGA-II, bi-objective knapsack (binary encoding), 3-objective JSS
  via NSGA-III, and a hypervolume-based operator comparison.

- Updates choosing-an-algorithm.md to reference the new operators in
  the single- and multi-objective decision tables, plus a noting
  NSGA-II/III's genericity over Vec<usize> and Vec<bool> decisions.

- SUMMARY.md and cookbook.md updated to list the new recipe.

docs/book/src/cookbook.md

@@ -19,7 +19,11 @@ project.
 - [Compare two algorithms on your problem](./cookbook/compare.md) —
   multi-seed harness pattern straight from `examples/compare.rs`.
 - [Optimize a permutation (TSP-style)](./cookbook/permutation.md) —
-  Ant Colony with a distance matrix.
+  the permutation operator toolkit (OX / PMX / CX / ERX + Inversion /
+  Insertion / Scramble), plus Ant Colony for distance-matrix TSP.
+- [Multi-objective combinatorial problems](./cookbook/multi-objective-combinatorial.md)
+  — bi-objective TSP, bi-objective knapsack (`Vec<bool>`), and
+  3-objective JSS via NSGA-II / NSGA-III.
 - [Constrain your search with `Repair`](./cookbook/constraints.md) —
   bounds, simplex projection, custom repair.
 - [Pick one answer off a Pareto front](./cookbook/pick-one.md) — the