fix(test): wait for kind cluster cleanup before recreating

Replace the fixed `sleep 20` with a polling loop that waits for
`kind get clusters` to report no clusters. The previous approach
was flaky on CI runners where Docker takes longer to tear down
cgroup hierarchies after `kind delete cluster`.

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

tests/k8s-deploy/run-deploy-test.sh

@@ -46,6 +46,18 @@ wait_for_log_output () {
 }
 
 
+wait_for_cluster_destroyed () {
+    for i in {1..60}
+    do
+        if ! kind get clusters 2>/dev/null | grep -q .; then
+            return
+        fi
+        sleep 2
+    done
+    echo "waiting for kind cluster cleanup: FAILED"
+    exit 1
+}
+
 delete_cluster_exit () {
     $TEST_TARGET_SO deployment --dir $test_deployment_dir stop --delete-volumes
     exit 1
@@ -227,9 +239,10 @@ fi
 
 # Stop then start again and check the volume was preserved
 $TEST_TARGET_SO deployment --dir $test_deployment_dir stop
-# Sleep a bit just in case
+# Wait for the kind cluster to be fully destroyed before recreating it.
-# sleep for longer to check if that's why the subsequent create cluster fails
+# Without this, the second 'kind create cluster' can fail with cgroup
-sleep 20
+# detection errors because Docker hasn't finished cleaning up.
+wait_for_cluster_destroyed
 $TEST_TARGET_SO deployment --dir $test_deployment_dir start
 wait_for_pods_started
 wait_for_log_output