Vela verified frontier: sidon-sets

Signed, replayable scientific-state archive for the 'sidon-sets' frontier, produced with the Vela protocol (https://github.com/vela-science/vela). Contains the full canonical event log, finding records, machine-checkable witness certificates, and the signed registry manifest. Re-verify offline with `vela check` (event-log replay) and `vela reproduce` (frozen exact verifiers re-check every witness). See VERIFY.md inside the bundle.