Decode a VIN to its graph identity

Why the VIN yielded no identity, from a closed vocabulary of eleven in three classes. The engine's refusals, written beside a row: WMI_UNKNOWN, PATTERN_UNKNOWN, UNKNOWN_MODEL_YEAR, INVALID_LENGTH, INVALID_CHARACTERS, CHECK_DIGIT_MISMATCH, NON_STANDARD_CHECK_DIGIT. The fold's own, for a refusal the engine gives no code for: NO_PATTERN_MATCH, MAKE_REF_GRAMMAR. And two minted at the READ, which answer a different question — not 'why could we not name this build' but 'why is there no row to read': UNSEEN_BUILD (the build is well-formed and has never been decoded — distinct from decoded and refused, and the one the refresh top-up mints next) and UNKEYABLE_VIN (the VIN projects onto no build code, so there is no key). Non-empty whenever valid is false; null exactly when valid is true. Typed as strings on the wire on purpose: the row classes are closed by a CHECK on ocean.identity.status_reasons and the read class by the API, so a new code is a deliberate change and never breaks a client parsing this field.