Constant DEFAULT_MAX_APP_EVENT_BYTES 

pub const DEFAULT_MAX_APP_EVENT_BYTES: usize = _; // 1_048_576usize

Default per-AppEvent payload cap consulted by Node::deliver_event. 1 MiB. Oversize payloads return DeliveryError::OversizePayload synchronously AND emit AppIngressError { kind: PerItemCapExceeded } on the bus.