Yup. Every time there's one of these threads I renew my call for GHA to have hooks where in-band build tools like nix, bazel, dagger, and friends can propagate

Yup. Every time there's one of these threads I renew my call for GHA to have hooks where in-band build tools like nix, bazel, dagger, and friends can propagate upward optimal information to be displayed in the web gui, in particular annotations and info about multiple tasks that run in parallel or series.