ci(pr-checks): run the staging drill's tests (#20)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

.gitea/workflows/pr-checks.yml

@@ -57,3 +57,7 @@ jobs:
       # not portable across the Node versions this project runs on.
       - name: Test the checker itself
         run: node --test scripts/checkPlugin.test.js
+
+      # The staging drill's pure parts (tools/drill/drill.js): its stall limit and fresh-data list.
+      - name: Test the staging drill
+        run: node --test tools/drill/drill.test.js