fix(ci): use runtime image for deploy step, add podGC to sensor

- Deploy step: use foxhunt-runtime image (cached on platform node) +
  curl kubectl, replacing bitnami/kubectl:1.31 which doesn't exist.
- Sensor: add podGC:OnPodCompletion and ttlStrategy to workflow spec
  (not inherited from WorkflowTemplate via workflowTemplateRef).

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

infra/k8s/argo/ci-pipeline-template.yaml

@@ -568,7 +568,7 @@ spec:
       nodeSelector:
         k8s.scaleway.com/pool-name: platform
       container:
-        image: bitnami/kubectl:1.31
+        image: gitlab-registry.foxhunt.svc.cluster.local:5000/root/foxhunt/foxhunt-runtime:latest
         command: ["/bin/sh", "-c"]
         resources:
           requests:
@@ -580,6 +580,11 @@ spec:
         args:
           - |
             set -e
+            echo "=== Installing kubectl ==="
+            curl -sLo /usr/local/bin/kubectl "https://dl.k8s.io/release/v1.31.4/bin/linux/amd64/kubectl"
+            chmod +x /usr/local/bin/kubectl
+            kubectl version --client
+
             echo "=== Rolling restart of service deployments ==="
             SERVICES="api trading-service ml-training-service backtesting-service trading-agent-service broker-gateway data-acquisition-service"
             for svc in $SERVICES; do

infra/k8s/argo/events/ci-pipeline-sensor.yaml

@@ -34,6 +34,10 @@ spec:
                 namespace: foxhunt
               spec:
                 serviceAccountName: argo-workflow
+                podGC:
+                  strategy: OnPodCompletion
+                ttlStrategy:
+                  secondsAfterCompletion: 3600
                 workflowTemplateRef:
                   name: ci-pipeline
                 arguments: