- Add create_game method that loads decks via DeckService, converts
CardDefinitions to CardInstances, and persists to Redis/Postgres
- Build card registry from only the cards in play (not all cards)
- Add GameCreationError exception and GameCreateResult dataclass
- Add creation_engine_factory for DI-based testing (no monkey patching)
- Add helper methods: _cards_to_instances, _build_card_registry
- Update tests with proper mocks for success, deck failure, engine failure
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>