fix: integrate PR #3314 review feedback

- ci(robocerebra): drop redundant hf auth login step (auth is
  already performed inside the eval step's container).
- ci(robocerebra): add Docker Hub login before the image build
  to pick up the authenticated rate limit.
- docs(robocerebra): align eval snippet with the CI command
  (observation size, camera_name_mapping, use_async_envs, device,
  empty_cameras=1).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/benchmark_tests.yml

@@ -333,6 +333,12 @@ jobs:
         with:
           cache-binary: false
 
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3 # zizmor: ignore[unpinned-uses]
+        with:
+          username: ${{ secrets.DOCKERHUB_LEROBOT_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_LEROBOT_PASSWORD }}
+
       - name: Build RoboCerebra benchmark image
         uses: docker/build-push-action@v6 # zizmor: ignore[unpinned-uses]
         with:
@@ -344,14 +350,6 @@ jobs:
           cache-from: type=local,src=/tmp/.buildx-cache-robocerebra
           cache-to: type=local,dest=/tmp/.buildx-cache-robocerebra,mode=max
 
-      - name: Login to Hugging Face
-        if: env.HF_USER_TOKEN != ''
-        run: |
-          docker run --rm \
-            -e HF_HOME=/tmp/hf \
-            lerobot-benchmark-robocerebra:ci \
-            bash -c "hf auth login --token '$HF_USER_TOKEN' --add-to-git-credential && hf auth whoami"
-
       - name: Run RoboCerebra smoke eval (1 episode)
         if: env.HF_USER_TOKEN != ''
         run: |