Operator 2026-06-17. Closes the prevb resolver gap: when the last-green
warm-canonical base version equals the PR head version, step back to the
newest published version strictly older than head (design A) instead of a
same-version no-op or a skip. Design B (canonical history for a green-verified
older base) saved to IDEAS. Auto-runs after regall (watchdog advances + switches
to opus).
