Function is_bunker 

pub fn is_bunker() -> bool

true iff the active account signs via a remote NIP-46 bunker. Hot-path helper for code that needs to branch on signer mode (e.g. parallelising gift-wrap signing harder when each call pays a round-trip).

Reserve this for genuinely NIP-46-relay-specific logic. For “we don’t hold the identity key on this device” gates (key export refusal, keyless-account feature availability) use is_keyless() instead — a NIP-55 account is keyless but not a bunker.