//!
//! # Basic Data Structures
//!
//! Fundamental, unversioned data structures that wrap the raw storage
//! implementations from `vsdb_core`, offering typed APIs for keys and values.
//!
//! - `Mapx` — `HashMap`-like, unordered.
//! - `MapxOrd` — `BTreeMap`-like, ordered by key.
//! - `MapxOrdRawKey` — ordered map with raw-byte keys (internal building block).
//! - `Orphan` — a single persistent value.
//! - `PersistentBTree` — a persistent B+ tree with copy-on-write structural sharing.
//!