fix(decisioning): TaskHandoff registry.fail/complete echo request context #1247

Job	Run time
Downstream import smoke (representative consumer symbols)	31s
Postgres conformance tests (Postgres 16)	1m 1s
v3 reference seller — pytest (respx-mocked upstream)	46s
AdCP storyboard runner — sales-proposal-mode (proposal_finalize)	1m 5s
AdCP storyboard runner — v3 reference seller (translator)	1m 21s
Validate schemas are up-to-date	3m 35s
Validate conventional commit format	7s
AdCP storyboard runner — examples/seller_agent.py	1m 26s
AdCP storyboard runner — examples/multi_platform_seller (PlatformRouter)	1m 37s
Test Python 3.12	3m 41s
Test Python 3.10	3m 39s
Test Python 3.11	3m 28s
Test Python 3.13	3m 25s
	25m 42s

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