Add simulated-data tests for karyotype (#700)

closes #700

Part of #689

What changed

• malariagen_data/anoph/karyotype.py - load_inversion_tags now accepts
  an absolute file path in addition to a package-resource filename. This allows
  tests to pass a dynamically-generated tag file on disk.

• tests/anoph/conftest.py -Ag3Simulator gains init_inversion_tags(),
  which picks tag SNP positions directly from the simulated SNP data (so they
  are guaranteed to exist in the fake genotype data) and writes them to a
  temporary CSV. The path is exposed as ag3_sim_fixture.inversion_tag_path.

• tests/anoph/test_karyotype.py - 22 tests covering all 7 Ag
  inversions (2La, 2Rb, 2Rc_col, 2Rc_gam, 2Rd, 2Rj, 2Ru):

  • test_load_inversion_tags — checks the returned DataFrame shape/columns/values
  • test_load_inversion_tags_not_implemented — asserts NotImplementedError when no path is set
  • test_karyotype — checks output DataFrame across multiple sample_sets values
  • test_karyotype_with_sample_query — checks filtering via sample_query