Function endpoint_payload_is_latency_sensitive 

pub fn endpoint_payload_is_latency_sensitive(payload: &[u8]) -> bool

Return true when an app-owned endpoint payload should retain priority-lane progress.

Embedders that stage packets before calling FipsEndpoint::send*_to_peer can use this to apply the same priority/bulk policy as the FIPS endpoint command queue without duplicating IP/TCP parsing.