docs: Phase D D10 structured agent contribution summary template -- failure-mode checklist, disconfirming pass, stop-condition gate, one-sentence verdict - #893

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, actions/setup-python@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/