Rate-limit evidence from a rate_limit_event during observed one-shot execution.
ClaudeWrapper.Query.execute/3 sends {reference, observation} to the
configured local observer as the CLI writes the event to stdout. This is
provider-reported state at that point in the run, not proof of completion or
a durable usage snapshot. Callers must correlate the reference with their
current invocation and decide how long the observation remains fresh.