Engram credential management with encrypted storage and YubiKey support.
This crate provides:
- Structured secret types (Login, ApiKey, OAuthApp, SshKey, Note, Environment)
- AES-256-GCM encryption for secrets at rest
- YubiKey HMAC-SHA1 challenge-response for key derivation
- Agent keys with permission scoping and revocation
- Audit logging for all secret access
- Recovery key system for lost YubiKey scenarios