Project one typed HttpExecutionObservation per logical V3 execution through a
closed composition-root projector: only registered diagnostic context keys and
bucketed values reach the sinks, and terminal non-abort failures now emit
exactly one api.request.failed telemetry event. Caller cancellation and scope
fencing record a diagnostic but never a failure event.
routeId becomes a required input at the installed operation-executor boundary
so the feature gateway's low-cardinality route identity survives to the sink.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
