docs(fleet-manager): document approving agent step-up requests - #48

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: arduino/setup-task@v2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Restore cache failed: Dependencies file is not found in /home/runner/work/docs/docs. Supported file pattern: go.mod