LLM-judge entailment verifier (D4). One structured call over the existing LLM
routing decides, for each answer clause, whether the cited-memory text supports it — no
new model or serving. Reuses the complete_json_schema/4 seam.
Faithful to the pipeline's LlmCore isolation, it DEGRADES to all-supported when the LLM is absent/incapable, on any error, timeout, or malformed result: a broken verifier must never block a reflect answer. Likewise a clause the model omits defaults to supported.