refactor(autoland): merge land runs as a stack through a plan optimization policy - #72

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/