feat: optional idempotency (ADR-0022) and per-URN schema validation (… #30

Job	Run time
Conformance suite in sync	5s
Python 3.9	25s
Static analysis (ruff + mypy)	43s
Python 3.12	22s
Python 3.10	18s
Python 3.11	17s
Broker integration (Redis · RabbitMQ · SQS)	1m 13s
Python 3.13	22s
CI green	4s
	3m 49s

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