On the non-gate paths a failed DLQ write escaped without recover(), so a later
session-wide acknowledge() could silently acknowledge the message. The message
is now acknowledged only after the DLQ write succeeds; otherwise the session is
recovered for redelivery and the error is reported via onError.

Runs the Kafka/Artemis integration tests against GitHub Actions service
containers on push to main and workflow_dispatch: handler failure to the
DLQ after MaxTries and the schema-version gate rejection. The tests skip
when the broker env vars are absent, and the job is not a required check.