Fill the manifest's master_key_verifier slot with an opaque one-way
value (scheme-prefixed, bound to the backup id and the KDF salt) so a
restore can detect a wrong operator-supplied master key before touching
any target state, and probe-decrypt every artifact as stored under the
backup KEK before the manifest may seal — digest equality alone only
proves the ciphertext landed intact. The payload decryption tail is
factored out and shared with the restore side so producer and consumer
cannot drift on the framing.
Also drops the stale KmsClient test import orphaned by the backend
refactor (#5501); the test suite did not compile without this.
overtrue
fe7b592e42