Gates every golden the project lists in .surfex.exs (Surfex.Goldens): the relation
status (RELATIONS.md) and any project goldens (Surfex.Surface). One CI line for all
of them.
mix surfex.goldens # check: fails on any drift
mix surfex.goldens --write # regenerate every golden, drifted or not--config PATH reads another file. The namespace citations are read under defaults to
the app's name camelized. The project is compiled only when an entry is project code;
the built-in Elixir scanner reads source and needs no compile.
Every failure of every golden is reported in one run. --write writes them all,
drifted or not, so a drift shows up in the diff, and succeeds: regenerating is how a
drift is resolved. Checking is what fails.