Pin GitHub Actions to full-length commit SHAs - #6

Process completed with exit code 1.

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@0717577d45739eb3c851188b29f50ed6c0b2194e, actions/setup-java@0f62d2ad8407a414cddd4790bed06fd9ebda0f56. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/