fix(gateway): raw finish_reason when not streaming - #3492

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: steebchen/action-auto-semantic-pull-request@main. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/