feat(intelligent-assistant): implement permission-denied UI for chat, notebooks, and MCP tools - #4604

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262, backstage/actions/changeset-feedback@2cd6978b476cbdc39fec48346f8b6ca13199dd6a. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/