fix(copilot): route responses-only models (grok-4.x, gpt-5.x) to /responses API - #1

ssh exited with code 101

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. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/