ci: run admin test partitions sequentially (parallel browsers stalled on the runner)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -71,7 +71,15 @@ jobs:
         run: cd ui/desktop && npx ember test --test-port 0
 
       - name: test admin ui
-        run: cd ui/admin && npx ember exam --test-port 0 --split=4 --parallel=1
+        # Partitions run one after another (one browser at a time): four
+        # concurrent headless browsers stalled on the small shared runners.
+        run: |
+          cd ui/admin
+          for p in 1 2 3 4; do
+            echo "::group::admin partition $p/4"
+            timeout 25m npx ember exam --test-port 0 --split=4 --partition=$p
+            echo "::endgroup::"
+          done
 
       - name: dependency audit
         # Fails on critical advisories only; remaining high/moderate advisories