Problem

The gateway protocol evolves in packages/gateway-protocol, but nothing checks that the mobile clients keep up. A new server event type ships and iOS/Android silently ignore it — the drift is invisible until a user-facing feature misbehaves.

Proposal

A CI-runnable check that derives the event/method inventory from the protocol schema and compares it against what each mobile client actually handles (the event dispatch in the iOS gateway transport and the Android GatewaySession/ChatController). Output: per-client list of unhandled event types, with an explicit allowlist for intentionally ignored ones so the check stays quiet until real drift appears.

Impact

Protocol/client drift becomes a red check at PR time instead of a field bug report; the allowlist doubles as documentation of what each client intentionally ignores.