feat(question_gen): add 5 question family specs with sampling constraints
Define QuestionFamilySpec, LeakTestProfile, SamplingConstraint dataclasses
and instantiate 5 families (RETRIEVAL/REASONING/ENUMERATION/VISUAL/SPATIAL)
targeting failure mechanisms M1-M5. Implement get_family_for_slot with
legal-type filtering + weighted random selection.
13 unit tests cover: full task-type coverage, skill_target uniqueness,
deterministic seeding, invalid input errors, and chi-square distribution.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
iomgaa
75e6d8c550