docs: salesagent → adcp Python SDK migration guide #1139

Job	Run time
Validate conventional commit format	8s
AdCP storyboard runner — examples/seller_agent.py	1m 17s
Downstream import smoke (representative consumer symbols)	26s
AdCP storyboard runner — v3 reference seller (translator)	1m 21s
Test Python 3.10	3m 38s
Validate schemas are up-to-date	3m 28s
AdCP storyboard runner — examples/multi_platform_seller (PlatformRouter)	1m 17s
Test Python 3.11	3m 24s
Postgres conformance tests (Postgres 16)	1m 6s
v3 reference seller — pytest (respx-mocked upstream)	39s
Test Python 3.13	3m 32s
Test Python 3.12	3m 15s
	23m 31s

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