/**
 * Transport seam for encrypted secrets-bundle sync.
 *
 * A `SyncBackend` moves opaque ciphertext envelopes to and from some remote.
 * It NEVER sees plaintext: encryption (`encryptBlob`) happens in `sync.ts`
 * before `putEnvelope`, and decryption (`decryptBlob`) happens after
 * `getEnvelope`. This mirrors the `KeychainBackend` storage seam
 * (`src/lib/secrets/index.ts`) but abstracts *transport* rather than at-rest
 * storage — so the high-level push/pull logic in `sync.ts` is decoupled from
 * any specific backend (Rush's api.prix.dev, a future Supabase driver, an
 * in-memory test double, …).
 */
export {};
