Update test workflow to upload coverage and post comment

.github/workflows/test.yml

@@ -15,3 +15,19 @@ jobs:
 
       - name: Build and test with Docker Compose
         run: docker compose run test
+
+      - name: Upload test coverage
+        id: coverage-upload
+        uses: actions/upload-artifact@v4
+        with:
+          name: code-coverage-report
+          path: coverage
+
+      - name: Post comment linking to artifact
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh pr comment ${{ github.event.pull_request.number }} \
+            --repo ${{ github.repository }} \
+            --body "Test coverage artifact: ${{ steps.coverage-upload.outputs.artifact-url }}"
+