Record local replay time for signed quorum witness checks

[aruintelligence]

Summary

• Sample the verifier's local clock once and use that exact instant for signed quorum witness freshness checks in both JavaScript and the project-authored Python verifier.
• Include witness_evaluation.evaluated_at (canonical UTC milliseconds) and clock_source: "local_system" on structurally checkable quorum replays, including failed witness checks.
• Document the unsigned, untrusted-clock boundary; preserve distinct valid, threshold_met, policy_met, witness_met, and inputs_met decisions.

Local verification

• 894 tests passed.
• Signed quorum JavaScript/Python comparison passed, including time interval and canonical formatting checks.
• Focused expiry boundary test showed one clock read and an expired witness rejection while quorum validity and saved threshold remained true.
• Proof, API stability, upgrade contract, installed-package consumer compatibility, CLI contract, package artifact, links, proof surfaces, verifier surfaces, and git diff --check passed.

These are project-controlled local checks. GitHub CI is pending; this does not establish independent certification or a trusted timestamp.