OSS-first docs
These docs teach the open system first: contracts, generated surfaces, runtimes, governance, and incremental adoption. Studio shows up as the operating layer on top, not as the source of truth.
`entityKind` is the built-in `ReferenceKindDefinition` for entity references. Each instance carries a `slug` (entity type key) and an `id` (instance identifier). The slug resolves to a `ContractEntitySpec` via `resolveEntitySpec(payload, registry)`, connecting RichReference governance (redaction, policy, audit) to the contracts-spec entity graph.