fix: refresh generated artifact provenance after #919

[tcconnally]

Summary

• refresh the committed perseus.py build-provenance marker to the exact source revision that produced the artifact
• keep the correction limited to the generated artifact; no source or contract behavior changes
• follow up on the merged feat: add versioned context contracts and admission controls #919 implementation without closing or widening that issue

Verification

• uv run --isolated --no-project --with pyyaml --with jsonschema --with pytest python scripts/build.py --check
• build smoke test passed
• focused provenance/doctor tests: 56 passed
• full repository gate: 2107 passed, 7 skipped, 5 warnings