Problem:\n- Several fixture directories are empty (fixes/, valid hooks/plugins/memory, invalid subdirs), and hooks fixtures are only referenced via include_str! in unit tests.\n\nExpected:\n- Either populate or remove empty fixture directories.\n- Ensure hook fixtures are exercised through CLI/integration flows, not only unit tests.\n\nAcceptance:\n- tests/fixtures has no empty placeholder dirs.\n- CLI validation over fixtures covers hook settings.json cases.