Add library-checker verification tests

25 tests against judge.yosupo.jp covering:
- Data structures: unionfind, point_add_range_sum, staticrmq,
  ordered_set, range_add_range_min
- Graph: scc, shortest_path, bipartitematching
- Tree: lca
- Number theory: factorize, primality_test, discrete_logarithm_mod,
  sqrt_mod, kth_root_integer, enumerate_primes, primitive_root,
  binomial_coefficient_prime_mod
- String: suffixarray, zalgorithm, number_of_substrings
- Convolution: convolution_mod
- Geometry: static_convex_hull
- Other: two_sat, longest_increasing_subsequence, find_linear_recurrence

Also adds GitHub Actions workflow for automated verification with PyPy.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>