spacedb-store 0.5.0

SpaceDB Layer 0 — the per-node storage primitive: an engine-agnostic, transactional, order-preserving typed key/value store (redb + in-memory engines) that everything in SpaceDB rests on. Phase 1 SpaceDB Mission, M1 / Slice 1. See 'docs/plans/(working) phase 1 spacedb mission.md'.