feat(layer-nerdctl): nested-pod posture + its R10 bed (Phase 4, v2) - #2

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/github-script@v7, actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

auto-merge arming did not settle — verdict is PASS, merge manually