pkvault → moved to ddyy/pk

pkvault now lives in the ddyy/pk monorepo at apps/pkvault. The full commit history was imported via git subtree, so every commit SHA from this repository is preserved in that repo's ancestry and remains auditable.

This repository is archived, not deleted, on purpose:

• The release pages here and their published page digests remain valid and resolvable forever — if you pinned a verify:page digest from a release in this repo, it still verifies.
• All tags are preserved.
• New releases are tagged pkvault-v<version> in ddyy/pk releases, starting with pkvault-v0.1.1.

No code or wire-format changes accompanied the move. See the changelog entry in apps/pkvault/CHANGELOG.md for the audit trail.