Function build_envelope_seed

pub fn build_envelope_seed(
    message_vault_passport: MessageVaultPassport,
    participants: &[impl ParticipantPublicKeys],
    key: &Key,
    credential_vaults: Vec<CredentialVault>,
    csprng: &mut impl CryptoRngCore,
) -> Result<EnvelopeSeed, CryptError>

Build an [EnvelopeSeed] containing all components needed for secure message delivery.

Assembles the complete envelope seed structure that includes BlindedPublicKeys for anonymous messaging, [CredentialVault]s for key distribution, and the encrypted [MessageVaultPassport].