extendReviewItemDueDate
Extend the current stage's due date (admin operator action, review.item.create — same pin as the service method). OPEN items only; newDueDate must be in the future. Rewrites the stage's PENDING due dates, recomputes expires_at (deliberately OVERRIDING the campaign due_at ceiling) + the wakeup, and records DUE_DATE_EXTENDED. Returns the updated admin item.
extendReviewItemDueDate(
id: ID!
newDueDate: DateTimeISO!
): ReviewItem!