Default OTLP endpoint points at an addon namespace that usually does not exist

Default OTLP endpoint points at an addon namespace that usually does not exist

manifests/ate-install/ate-otel-config.yaml defaults to http://opentelemetry-collector.gke-managed-otel.svc.cluster.local:4317. On any cluster without GKE's managed OTel addon enabled - the default gke-managed-otel namespace does not exist, so every component fails to resolve the collector once a minute, forever, and telemetry is silently dead. It presents as a networking fault rather than a missing dependency.

The installer rewrites the ConfigMap, so patching it after install is silently reverted. The override has to go in at install time via ATE_OTLP_ENDPOINT, which hack/install-ate.sh already honours.

Ask: default to no exporter, or make the install refuse when the endpoint's namespace is absent.