refactor: remove stale ManagedModel message management and AgentGraphResult type #657

Job	Run time
server-ai-windows (3.14)	24s
server-ai-langchain-linux (3.14)	23s
server-ai-windows (3.11)	28s
server-ai-windows (3.10)	32s
server-ai-windows (3.13)	19s
server-ai-optimization-windows (3.10)	20s
server-ai-langchain-linux (3.13)	21s
server-ai-langchain-linux (3.10)	20s
server-ai-windows (3.12)	25s
server-ai-optimization-windows (3.12)	17s
server-ai-langchain-linux (3.11)	22s
server-ai-optimization-windows (3.11)	15s
server-ai-langchain-linux (3.12)	17s
server-ai-linux (3.10)	11s
server-ai-optimization-linux (3.13)	11s
server-ai-langchain-windows (3.12)	18s
server-ai-optimization-linux (3.11)	13s
server-ai-langchain-windows (3.10)	25s
server-ai-linux (3.11)	12s
server-ai-linux (3.12)	9s
server-ai-optimization-linux (3.14)	16s
server-ai-langchain-windows (3.11)	33s
server-ai-openai-windows (3.10)	22s
server-ai-openai-windows (3.14)	26s
server-ai-optimization-linux (3.12)	13s
server-ai-openai-windows (3.13)	23s
server-ai-optimization-linux (3.10)	11s
server-ai-optimization-windows (3.14)	21s
server-ai-linux (3.14)	12s
server-ai-openai-windows (3.12)	34s
server-ai-langchain-windows (3.13)	18s
server-ai-langchain-windows (3.14)	22s
server-ai-openai-linux (3.12)	22s
server-ai-optimization-windows (3.13)	21s
server-ai-linux (3.13)	6s
server-ai-openai-linux (3.10)	24s
server-ai-openai-windows (3.11)	22s
server-ai-openai-linux (3.14)	21s
server-ai-openai-linux (3.11)	22s
server-ai-openai-linux (3.13)	21s
	13m 12s

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