The wrong-answer firewall for the candidate-graph parser topology.
A CandidateOperation carries an Operation plus source-span provenance
for every content slot the parser claimed (verb, value, unit, actor,
transfer target, comparison reference). roundtrip_admissible() checks
each slot grounds in the source span AND the matched verb is
registered for the claimed kind.
Two consequences:
- A regex that mis-reads 'loses' as add fails (loses not in ADD_VERBS).
- A regex that hallucinates a number/unit not in source fails to ground.
KIND_TO_VERBS is the new single source of truth for {kind -> verbs};
P2 will refactor math_parser to consume it. Verb tables are
permissive by design (much wider than current narrow regex tables)
because the filter rejects wrong candidates downstream — narrowness
is no longer the safety mechanism.
Deterministic: pure byte/regex containment. No randomness, no
learning, no approximation. Preserves wrong==0, trace_hash byte-
equality, replay determinism.
