Epic: Eventing, narration, and the control plane #449

Specs: 2.8-eventing-infrastructure.md ·
2.7-control-plane.md
Plan: step 50

The run's steer-and-observe surface is three orthogonal pieces — control commands, event streams, and
narration — sharing one seam. The command surface landed; the other two did not.

Design is solidified: an app-agnostic bus with a hook interface, three streams mapping onto OpenTelemetry
(narration and diagnostics as Logs by severity and audience, op-events as Spans forming the execution
tree, results as the deliverable), with the Collector as router and the control plane as one sink among
several rather than the event owner.