[pennycoders]

With the default values (no otel.endpoint), ate-api-server, atelet, ate-controller and k8s-credential-provider push traces and metrics to the SDK default, localhost:4317, and log a connection error about once a minute.

• A signal that is enabled but resolves no endpoint now renders OTEL_<SIGNAL>_EXPORTER like a disabled one. Metrics get prometheus rather than none: it stops the push but keeps every scraped endpoint, while none would also close atecontroller's :8080.
• k8s-credential-provider includes substrate.otel.env like the other components. It had no env, so no value could configure or stop its export.
• The same helper change goes into the copy in substrate-atelet.
• README and values.yaml no longer say the Go components ignore otel.traces.enabled; serverboot honors OTEL_TRACES_EXPORTER.

With otel.endpoint set, the rendered env of the existing components is unchanged; only the credential provider gains its env.

Tested: helm lint on the four charts, hack/render-manifests.sh --check, helm unittest charts/substrate (three new cases, which fail without the template change), hack/verify-all.sh, and go test for the packages that render the chart.

Fixes #76

AI use: AI-assisted, I reviewed and tested it.

• Tests pass
• Docs updated