Default Victoria Metrics k8s dashboards were filtering on 'cluster' label
which only contained 'observability'. Our metrics use 'cluster_environment'
label which contains the actual cluster values: dev, edp, observability.
Hub defaultRules groups kubernetesSystemControllerManager, kubeScheduler, and
kubernetesSystemScheduler used wrong key 'enabled: false' — chart expects 'create: false'.
This caused KubeControllerManagerDown/KubeSchedulerDown to fire as false positives
because OTC CCE managed k8s does not expose control plane for scraping.
Dev local vmagent had empty externalLabels, so backup-alert rules evaluated by local
vmalert had no cluster_environment label on kube_job_status_failed metrics. Added
cluster_environment=dev to match what the vm-client-stack vmagent adds for hub shipping.
