Function frame_carries_ephemeral_credentials 

pub fn frame_carries_ephemeral_credentials(value: &Value) -> bool

True when a broadcast frame was stamped with EPHEMERAL_BROADCAST_MARKER by record_event — i.e. it carries broadcast-only pairing secrets (QR payloads, pair codes) deep-merged into attributes.

Every consumer of the shared broadcast bus (the gateway SSE stream, the RPC logs/subscribe forwarder) uses this to fail closed on the credential unless it can prove its subscriber is authenticated.