fix(ci): re-chmod artifacts after eval to fix unreadable files

Files created by user_lerobot inside the eval container inherit a
restrictive umask, making them unreadable by the runner after the
container exits. Add a post-eval 'docker run --user root' chmod step
so upload-artifact can find the video files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/benchmark_tests.yml

@@ -133,6 +133,16 @@ jobs:
                 --output_dir=/artifacts
             "
 
+      - name: Fix Libero artifact permissions
+        if: always()
+        run: |
+          # New files written by user_lerobot inside the container inherit a
+          # restrictive umask; re-chmod as root so the runner can read them.
+          docker run --rm --user root \
+            -v /tmp/libero-artifacts:/artifacts \
+            lerobot-benchmark-libero:ci \
+            bash -c "chmod -R 777 /artifacts"
+
       - name: Upload Libero rollout video
         if: always()
         uses: actions/upload-artifact@v4
@@ -205,6 +215,14 @@ jobs:
                 --output_dir=/artifacts
             "
 
+      - name: Fix MetaWorld artifact permissions
+        if: always()
+        run: |
+          docker run --rm --user root \
+            -v /tmp/metaworld-artifacts:/artifacts \
+            lerobot-benchmark-metaworld:ci \
+            bash -c "chmod -R 777 /artifacts"
+
       - name: Upload MetaWorld rollout video
         if: always()
         uses: actions/upload-artifact@v4