The refusal-first, provenance-carrying structure the field-decode produces and
the domain reasoners project from. Sibling of the binding-graph (ADR-0132) but
carries GENERAL meaning (entities + n-ary named relations), neutral to the
engine substrate (no algebra/field/numpy import), and imposes NO acyclicity
(relation cycles are well-formed, unlike the equation DAG).
Refusal-first construction: non-identifier ids, empty predicates, zero-arity
relations, duplicate entity ids, and relations referencing unknown entities all
refuse at construction. Deterministic to_canonical_string for replay/hashing.
Polarity (negated) is first-class. kind/predicate carry no closed vocab yet
(defer-substrate-vocab).
Phase 2a foundation under Path alpha (field standing-hand + refusal floor); the
field-decode -> refusal-floor -> MeaningGraph reader is the next increment.
18 new tests (each bites under its named violation); architectural invariants +
capability index green.
