Add initial test infrastructure covering:
- skillopt/utils/scoring.py (compute_score, skill_hash)
- skillopt/utils/json_utils.py (extract_json, extract_json_array)
- skillopt/types.py (Edit, Patch dataclass serialization)
All tested functions are pure/deterministic with no LLM dependencies.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
