keyfunc mnemonic prints a child mnemonic derived from the main one with
BIP-85's own mnemonic application, in English, at 12, 18 or 24 words.
Its entropy is the BIP-85 entropy cut to the length the word count
needs, which is what that application asks for, so it does not go
through the generator the other key types read their bytes from. The
BIP-85 specification's own test vectors for the application are the
tests.
Two pieces the derivation package already had inside one function are
now named: the master key a mnemonic stands for, and the refusal of a
key index that has no hardened child. Both key types call them.
Model: opus-5
