std::observeRuntime observability reads.
readRead one canonical metric by name.
Returns None when the metric name is unknown.
scrapeRender the current metric registry in scrape text format.
seriesRender the canonical metric series names, one per line.
barrierReturns an error when called from an actor turn or when the native runtime's bounded 30-second internal wait expires.
ObserveErrorWait for actor-turn observe attribution visible to series/scrape.
ActorTurnTimedOut