fix(ci): add LD_LIBRARY_PATH for CUDA runtime, fix git checkout

1. CUDA_ERROR_STUB_LIBRARY: ci-builder image has CUDA stubs ahead of
   real NVIDIA driver libs in LD_LIBRARY_PATH. Prepend
   /usr/local/nvidia/lib64 (device-plugin mount) so real driver is
   found first.
2. Git checkout: `git checkout --force main` stays on local main
   without pulling. Add `git reset --hard origin/$REF` to fast-forward
   branch to latest remote commit.

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

infra/k8s/argo/gpu-test-pipeline-template.yaml

@@ -131,6 +131,8 @@ spec:
             value: /data/test-data
           - name: RUST_LOG
             value: info
+          - name: LD_LIBRARY_PATH
+            value: /usr/local/nvidia/lib64:/usr/local/cuda/lib64:/usr/local/cuda/extras/CUPTI/lib64
         volumeMounts:
           - name: git-ssh-key
             mountPath: /etc/git-ssh
@@ -179,6 +181,8 @@ spec:
                 echo "=== Updating checkout ==="
                 git fetch origin
                 git checkout --force "$REF"
+                # If REF is a branch, fast-forward to origin
+                git reset --hard "origin/$REF" 2>/dev/null || true
                 git clean -fd
               fi
             else