Foundation types for the selene-db ISO/IEC 39075:2024 GQL property graph engine.
This crate is the dependency root: every other selene crate transitively
depends on it. Per D8, selene-core has zero dependencies on other selene
crates. The mandatory data types of ISO GQL minimum conformance live here
(STRING, BOOLEAN, INT, FLOAT); composite, temporal, and reference
value types are also normatively defined in Spec 02 and implemented here.
The crate now also carries the composite containers,
schema model, origin metadata, and WAL change payload
types needed by downstream crates.
See Spec 02 for the full data model specification.