feat(decisioning): AuthInfo.from_verified_signer — bridge to RFC 9421 verifier #907

Job	Run time
Validate conventional commit format	7s
Downstream import smoke (representative consumer symbols)	33s
Validate schemas are up-to-date	3m 26s
Postgres conformance tests (Postgres 16)	1m 2s
AdCP storyboard runner — examples/seller_agent.py	45s
Test Python 3.11	3m 12s
Test Python 3.12	3m 14s
Test Python 3.10	3m 12s
Test Python 3.13	3m 1s
	18m 32s

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