Pin GitHub Actions to full-length commit SHAs - #73

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@1bd1e32a3bdc45362d1e726936510720a7c30a57, actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, microsoft/setup-msbuild@6fb02220983dee41ce7ae257b6f4d8f9bf5ed4ce. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/