default = [fjall, graph-algo] is missing mneme-engine. Pulling mneme the obvious way gives graphe session store and episteme pipeline without the Datalog knowledge store or typed query builder. For a crate whose purpose is memory engine, shipping a default that excludes the engine is a footgun. The coexistence test (engine_and_sqlite_session_store_coexist) existing at all is the tell. Either make mneme-engine default, or rename it to clarify what it gates (e.g. datalog-query).
default = [fjall, graph-algo] is missing mneme-engine. Pulling mneme the obvious way gives graphe session store and episteme pipeline without the Datalog knowledge store or typed query builder. For a crate whose purpose is memory engine, shipping a default that excludes the engine is a footgun. The coexistence test (engine_and_sqlite_session_store_coexist) existing at all is the tell. Either make mneme-engine default, or rename it to clarify what it gates (e.g. datalog-query).