feat: rebuild #106-110 on current main (list_namespaces/list_service_accounts, expected_principal, console provider picker+wiring, fleetsK8sToml.ts) - #115

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/