Review of vault crate against all architecture specs. Fixed 5 deviations:
1. EncryptionKey: removed Clone (now move-only per spec), added redacting Debug
2. EncryptionKey::new made private (cfg(test)), added pub(crate) key_bytes()
3. encrypt/decrypt made pub(crate) per encryption.md, low-level crypto tests
moved from integration to unit tests
4. CachedKey refactored to wrap DerivedKey with cached_at/last_accessed fields
per service.md, with key_type()/private_key()/public_key() accessors
5. Mnemonic::to_seed() unwrap() eliminated by storing validated Bip39Mnemonic
(enabled bip39 zeroize feature for proper zeroization)
All 10 drift items verified resolved. 105 tests pass; clippy clean.
Refs: docs/architecture/crates/vault/README.md (review checklist)
glm-5.2
d7d879a3fa