mc#798 drift-detect F3a/F3b: staging branch protection requires only
sop-checklist/all-items-acked, not sop-tier-check or Secret scan.
- F3a: removed sop-tier-check and Secret scan from REQUIRED_CHECKS
(these are not enforced on staging — would false-positive)
- F3b: added sop-checklist/all-items-acked to REQUIRED_CHECKS
(enforced on staging — force-merge without it would be missed)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>