refactor: consolidate prober logic into shared helper and add test-testid attributes to core UI elements

.github/workflows/prober-docker.yml

@@ -26,6 +26,12 @@ jobs:
       - name: Pull Docker image
         run: docker pull ghcr.io/pewu/topola-viewer:latest
 
+      - name: Record image digest
+        run: |
+          DIGEST=$(docker inspect --format='{{index .RepoDigests 0}}' ghcr.io/pewu/topola-viewer:latest)
+          echo "Testing Docker image: $DIGEST"
+          echo "::notice title=Docker Prober::Testing image $DIGEST"
+
       - name: Run container
         run: |
           docker run -d -p 8080:8080 -e STATIC_URL=test.ged \
@@ -33,14 +39,6 @@ jobs:
             --name topola-prober-${{ github.run_id }} \
             ghcr.io/pewu/topola-viewer:latest
 
-      - name: Wait for container to be ready
-        run: |
-          for i in $(seq 1 30); do
-            if curl -sf -o /dev/null http://localhost:8080/; then break; fi
-            sleep 1
-          done
-          curl -sf -o /dev/null http://localhost:8080/
-
       - name: Use Node.js
         uses: actions/setup-node@v4
         with:
@@ -67,6 +65,14 @@ jobs:
         if: steps.cache-playwright.outputs.cache-hit != 'true'
         run: npx playwright install chromium
 
+      - name: Wait for container to be ready
+        run: |
+          for i in $(seq 1 30); do
+            if curl -sf -o /dev/null http://localhost:8080/; then break; fi
+            sleep 1
+          done
+          curl -sf -o /dev/null http://localhost:8080/
+
       - name: Run prober
         env:
           PLAYWRIGHT_HTML_REPORT: playwright-report/prober