fix: reconcile prunes by GitHub PR state, not KV — runs on the preview nodes as-is (v0.3.0) [review, do not merge yet] - #38

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/