Typed Event Surface

Event and webhook surfaces are described by a contract, so an agent that must react to state changes has a typed surface rather than example payloads. RENAMED AND WIDENED IN 0.9 — it was `asyncapi_events` and read only the asyncapi/ directory, which named the artifact rather than the capability and scored a provider false for describing their events the other legal way. A webhook can be described in OpenAPI: 3.1 added a top-level `webhooks` object and `callbacks` predates it. In this catalog 125 providers do exactly that — 87 via `webhooks` across 2,218 events, 39 via `callbacks` — against ZERO who publish AsyncAPI. Both count, equally: the dimension asks whether an agent can read the event surface, not which specification the provider chose to write it in.