Retain all test artifacts

When testing ephemeral tests, the `ref` directory is temporary and not populated persistently.

This changes the archive action to upload all artifacts regardless of the test kind in use to ensure they are included for debugging.

Author: tingerrr

.github/workflows/tests.yml

@@ -60,6 +60,7 @@ jobs:
           path: |
             tests/**/diff/*.png
             tests/**/out/*.png
+            tests/**/ref/*.png
           retention-days: 5
 
       - name: Build docs