fix(protocol): sanitize LISH manifests in both wire directions

[lukyrys]

Keeps node-local LISH state (directory, finalDirectory, chunks) out of manifests in both wire directions.

• outgoing getLish responses stripped only directory and chunks — finalDirectory, a local filesystem path set while a LISH downloads into temp, leaked to remote peers
• incoming manifests were trusted as-is: a malicious peer could set finalDirectory to redirect the post-download move to a path of its choosing, or pre-flag chunks as already downloaded so they would never be fetched
• both directions now go through a single toManifest() helper at the trust boundary, with unit tests pinning the stripped fields
• the downloader preserves its own locally configured move target when importing a manifest, since the sanitized manifest never carries one