Relay 0.10 starts gen_ai trace/log/metric export on its own whenever an
active configuration meets an OTEL_EXPORTER_OTLP_* endpoint in the process
environment, and those spans carry prompt and response messages. The
legacy HERMES_NEMO_RELAY_ATIF/ATOF variables never exported OTLP, so the
generated relay-plugins.toml now pins opentelemetry.enabled = false.
Also restore the discovery-only test's DISABLED-state assertions: they
pass on 0.10 and only trip on a host with a machine plugins.toml.