Promotes the verify-time enforcement decision that accreted as four chronological addenda on ADR-550 (#1259/#1279/#1346/#1278) into a single first-class architecture-of-record. ADR-550 keeps the spec-phase contract; this ADR owns the test-tier enforcement producer (locate -> machine-prove-fail-first -> run -> dispose) in src/prohibition-enforcement.cts.
Verified against live src/*.cts: the green AND-gate lives in runProhibitionEnforcement, the empty-file vacuity guard is isNonVacuousNodeTestPass (red-side is isNonVacuousNodeTestRed), and the ADR-857 pointer cites the real 'Verification substrate vs. plug-in tier' section / decision #6.
Closes#1606.
