Replaces per-pattern negation lists: if ANY negation token (not, no, never,
cannot, cannot, will not, has not, is not, no longer, unable, decline,
regret, unfortunately) appears anywhere in the mail, an approval
classification downgrades to needs_review. Approval requires a mail with
zero negations. The LLM prompt braces stay escaped (round-1 fix retained).
tests: the six mandated sentences all classify non-approval.