test(critic-fixes): address brittleness, over-mocking, and missing edge cases (#20)

test(wave-4): LLM orchestration tests for eligibility, intake, and research (#19)

test(wave-3): deterministic eligibility and trials_api tests (#18)

test(wave-2): add pure-function tests for models and prompts (#17)

test(wave-1): add test infrastructure and conftest.py (#16)