Enum representing supported key derivation methods.
HKDF (HMAC-based Key Derivation Function) - RFC 5869
PBKDF2 (Password-Based Key Derivation Function 2) - RFC 8018
Scrypt - RFC 7914
Argon2id - RFC 9106 (default, most secure for passwords)
SSH Agent - Uses SSH agent for key derivation
Enum representing supported key derivation methods.