CI: test and build the shell's programs - #1

Process completed with exit code 1.

secret SNAIDHM_DEPLOY_KEY is not set: snaidhm is private and this build depends on it (a read-only deploy key on almide-graphics/snaidhm)

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/