Add an AMQP 0.9.1 transport example
KL
2mo ago+1140+1140+0123456789012345678901234567890123456789-4-4-0123456789
Review scope
Stacked on #3520 for the shared broker harness and CI setup. This diff contains only the AMQP 0.9.1 adapter, RabbitMQ configuration, examples, configuration tests, and AMQP documentation; there are no MQTT or gRPC implementation changes.
The existing review correction for cross-principal injection is preserved: dedicated direct exchanges replace default-exchange publication. Broker recording/coverage, broader failure validation, and production TLS authorization remain open merge gates.
Validation
Six AMQP configuration tests and pre-commit pass after the split; the dedicated CI job also runs the live broker programs.
AI Disclaimer
This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.