[temp][do not merge] probe: toolchains from xlings 2026.10.15.4 without mcpp fixups, borrowed payloads by link/junction, #809 under mcpp - #810

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/