The three OpenTelemetry signals #504

Epic: #449

Spec: 2.8 §Mapping to OpenTelemetry

The three streams land on three different OTel signals, not one. Attribute names are frozen against
semconv 1.43.0, and the invented ones are already dropped -- event.category, stream: status|result,
log.classification. Anything genuinely devlore-specific must be namespaced devlore.* with
justification.

The unifying mechanism: operational events as spans create the trace context that stitches narration and
diagnostics to the exact node.