Let heartbeats re-register testrunners the server has forgotten - #272

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@5ef0c079ce82195b2a36a210272d6b661572d83e. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/