Propagate top-level historyDbPath into historyStore.config so it
survives config merging, default the memory vector store to
~/.mem0/vector_store.db instead of process.cwd(), auto-create parent
directories for file-backed SQLite databases, and remove dead code
in the Memory constructor.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
