fix(train): use correct Argo Events label selector for CI workflow lookup

Argo Events labels workflows with events.argoproj.io/trigger, not
workflows.argoproj.io/workflow-template. Fixed find_ci_workflow() so
ci-train preset can actually find CI pipeline runs.

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

infra/scripts/train.sh

@@ -172,10 +172,10 @@ find_ci_workflow() {
   local sha="$1"
   local short_sha="${sha:0:8}"
   # List recent ci-pipeline workflows and find the one matching our commit.
-  # Argo labels the workflow with the template name; we also grep for the SHA
-  # in the workflow spec parameters.
+  # Argo Events labels workflows with events.argoproj.io/trigger (not
+  # workflows.argoproj.io/workflow-template), so use that selector.
   kubectl -n "${NAMESPACE}" get workflows \
-    -l "workflows.argoproj.io/workflow-template=ci-pipeline" \
+    -l "events.argoproj.io/trigger=ci-pipeline" \
     -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.phase}{"\t"}{range .spec.arguments.parameters[*]}{.name}={.value}{","}{end}{"\n"}{end}' \
     2>/dev/null \
     | grep "commit-sha=${sha}\|commit-sha=${short_sha}" \