test(graph): add subject relation expansion depth limits and cycle detection invariant tests - #3151

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: step-security/harden-runner@df199fb7be9f65074067a9eb93f12bb4c5547cf2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/