docs: promote three docs-audit technical-debt findings to issues #285-#287 - #288

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4, actions/checkout@v4, actions/setup-dotnet@v4, actions/upload-artifact@v4, microsoft/setup-msbuild@v2, nuget/setup-nuget@v2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/