Add the ⑥ regression gate that replays every reviewed validation_fixture bad case
through the real embedded PreParse pipeline and asserts the canonical outcome
(accepting either semantic rewrite or native real-flag acceptance, failing only
on a genuine unknown-flag hallucination). Add check-param-concepts.sh (dictionary
schema/loader invariants) and check-param-alias-cooccurrence.sh (full-tree
co-occurrence scan), and wire all three into make policy.