CAIN-42 Evolution 68 evidence bundle v5
Verify offline:  python3 verify_e68_offline.py <bundle-dir> [--authority-pub <b64>]
The bundle is signed by the authority key in manifest.json. Pin that key out of band for trust.
Anchoring: see anchoring.json. A local-only bundle is not externally anchored.
Artifacts are content-addressed; verify_e68_offline.py checks every digest, every worker result
signature, every ticket and grant signature, the event slice, and that no producer verified itself.