fix(tests): Missing artifacts (include-hidden-files) (#699)

`upload-artifact` updated behavior: Hidden Files will be excluded by
default
actions/upload-artifact#602

Need to include 
```yaml
include-hidden-files: true
```

.github/workflows/ci-core.yml

@@ -33,6 +33,7 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: "coverage-artifact-${{ matrix.python-version}}"
+          include-hidden-files: true
           path: ".coverage.*"
           retention-days: 1
       - name: Run doctests