feat: add messaging transport rollout

tests/conftest.py

@@ -1,7 +1,12 @@
 """Shared test fixtures.
 
-PostgreSQL integration tests are gated on TREX_POSTGRESQL_TEST_DSN; when it
-is unset they are skipped (unit/API tests still run via in-memory adapters).
+Infrastructure integration tests are gated on env vars:
+  - TREX_POSTGRESQL_TEST_DSN   : PostgreSQL repository/outbox/migration tests
+  - TREX_RABBITMQ_TEST_URL     : RabbitMQ transport + intent RPC E2E tests
+  - TREX_KIS_BROKER_*           : KIS sandbox round-trip test
+
+When a gate is unset the corresponding tests are skipped; unit tests
+(in-memory adapters, stub transport) always run.
 """
 from __future__ import annotations