ci(analyzer): adopt liveness primer for all pull requests

[duriantaco]

Summary

• Document Matthew Digman’s liveness_primer as Skylos’s official real project regression testing tool.
• Run the existing primer CI check for all PRs, including draft and docs only PRs.
• Explain how to review reports and use them alongside labeled benchmarks. Also keep existing primer pin

Tests

pytest test/test_liveness_primer_workflow.py test/test_corpus_ci.py test/test_regression_delta.py
test/test_cicd_workflow.py test/test_ai_pr_diff_rules.py test/test_github_actions_security.py

[mcdigman]

Thanks @duriantaco!