fix(infra): make gpu-warmup tolerant of missing nvidia-smi

nvidia-smi is driver-mounted by the GPU operator, which may not be
ready when the warmup pod starts on a fresh autoscaled node. The
warmup's purpose is just triggering autoscale, not GPU validation.

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

infra/k8s/argo/training-workflow-template.yaml

@@ -83,8 +83,8 @@ spec:
             template: upload-results
             dependencies: [evaluate]
 
-    # GPU warmup: triggers H100 autoscale during compilation so the node
-    # is ready when hyperopt starts. Exits immediately after nvidia-smi.
+    # GPU warmup: triggers GPU node autoscale during fetch-binary so the node
+    # and NVIDIA device plugin are ready when hyperopt starts.
     - name: gpu-warmup
       nodeSelector:
         k8s.scaleway.com/pool-name: "{{workflow.parameters.gpu-pool}}"
@@ -102,7 +102,7 @@ spec:
         args:
           - |
             echo "GPU warmup: triggering node autoscale..."
-            nvidia-smi --query-gpu=name,memory.total --format=csv,noheader
+            nvidia-smi --query-gpu=name,memory.total --format=csv,noheader 2>/dev/null || echo "nvidia-smi not yet available (driver still mounting)"
             echo "GPU node ready, exiting to free resources"
       resources:
         requests: