Manifest Signature

- Instead of signing individual deltas, you can sign a **digest of multiple journal entries**. - Useful for exporting or snapshotting trusted versions. - The manifest may include: - List of delta hashes - Full page hash - Page title - Version ID Fields: - `sig_type`: `"manifest-signature"` - `entry_hashes`: array of SHA256 hashes - `signed_at`: UTC timestamp - `signature`: signed manifest hash