entropyToBip39Seed

Deterministic chain from BIP-39 entropy to BIP-39 seed.

Public so cross-module orchestrators (e.g. SigilSession in :sdk:wallet-seed that holds a freshly-derived PRF output and needs the corresponding wallet seed without running another PRF ceremony) can call it directly. The function is pure and deterministic — input bytes alone determine the output; no security-sensitive state is exposed beyond what the caller already holds.

Returns the standard BIP-39 64-byte PBKDF2 seed (see BIP39.mnemonicToSeed).

Caller MUST wipe the returned ByteArray once the consumer has copied it — same contract as deriveBip39Seed and PlaintextSeed.bip39Seed.