2026.10.31.1: features in every envelope, program in self env; #868; #866/#867 follow-ups; canary build steps; --pkg-format polyglot; ldflags files as link inputs - #869

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache/restore@v4, actions/checkout@v4, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/