Define the LLM adapter interface in backend/engine/adapters/base.py with
async methods complete(), list_models(), and test_connection(). The
AdapterResponse dataclass holds response text, token counts, latency,
model name, and raw metadata. Includes 11 tests covering instantiation
guards, concrete subclass behavior, and dataclass semantics.
Set up all directories from the spec's Project Structure section:
- backend/ with routers/, engine/adapters/, engine/scorers/, mcp/,
websocket/, tests/ (all with __init__.py)
- frontend/src/ with pages/, components/, api/ (.gitkeep)
- docker/ (.gitkeep)
- alembic/versions/ (.gitkeep)
