fix(run): fail fast on incompatible handoff settings with server conversation#2457

OiPunk wants to merge 4 commits intoopenai:mainopenai/openai-agents-python:mainfrom

OiPunk:codex/openai-agents-2151-server-conversation-handoffOiPunk/openai-agents-python:codex/openai-agents-2151-server-conversation-handoffCopy head branch name to clipboard