Pin code generation and bring renovate.json to the org baseline - #1733

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: arduino/setup-protoc@c65c819552d16ad3c9b72d9dfd5ba5237b9c906b. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/