Harden artifact gate sync after release

[Evilander]

This is a small post-release hardening patch from the final audit.

• Runs paper:sync inside test:artifacts before regenerating arXiv and paper bundles.
• Runs paper:verify at the end of test:artifacts, so volatile benchmark outputs cannot drift from paper claims unnoticed.
• Leaves the published v1.0.0 tag untouched; this is a forward hardening PR on master.

Local verification from the clean audit clone:

• npm run test:artifacts passed.
• npm run typecheck passed.
• npx vitest run tests/guardbench.test.js passed: 73 tests.