downloads of deck fails on OS X runners.

The download of deck release fails with a 404 when the github runner is running on os x machine, as deck releases a universal package for os x.
It can be fixed by setting the arch parameter to "all" when the os is "darwin"

Start by locating the download logic used by the setup-deck GitHub Action and trace how the runner OS determines the release architecture. Reproduce the darwin case or inspect its request parameters, then verify that OS X runners resolve the deck release successfully without a 404.

Written by the indexing model from the issue text.