Publishes one integration event: builds the envelope from the caller's already-typed payload and hands it to broker.publish on the definition's topic.

The definition's parse function is deliberately NOT run here. parse is a narrowing function unknown → T, and a realistic one (a schema with defaults, coercion, or stripping) returns a different object than it was given — running it on publish would silently change what the producer asked to send. It also would not buy the guarantee it appears to: what the consumer parses is the value after a JSON round trip, which this call has not seen. The consequence is honest and documented: a producer CAN publish a payload its own consumers reject, and that surfaces at the consumer as a reason: 'parse' rejection.