test: Restructure test directory with unit/ and local_fixtures/
Create test/unit/ subdirectory and move api_tests/ into it, establishing the layout required for Phase A3 unit tests. Add test/local_fixtures/ package with ConfigMemoizedCache mixin to clear lru_cache state between tests, preventing cross-test pollution when config.py is introduced.
Generated-By: claude-code sonnet 4.6 Change-Id: I4c50e9c0ebe6d81f112a49d69fc7a66ddd04ed8a Signed-off-by: Sean Mooney work@seanmooney.info