/**
 * `subscribeEvent` fans one WS subscription out to N listeners.
 *
 * Measured on the viewer's boot: ~40 tRPC subscriptions before first paint,
 * of which 24 were twelve camera cards subscribing to the SAME two motion
 * categories and filtering by deviceId inside their own callbacks. Each was a
 * separate handshake on a transport that does not batch.
 *
 * The tests exercise the real `System` with a stubbed tRPC client, so
 * what is asserted is the number of `live.onEvent.subscribe` calls the SDK
 * actually makes — not a mock of the deduping itself.
 */
export {};