[appkit plugin] [5/x] Add chat server plugin to @databricks/appkit-agent #603

Job	Run time
format	11s
typechecking for integrations/dspy	14s
typechecking for .	10s
ruff check for integrations/openai	10s
ruff check for databricks_mcp	13s
typechecking for databricks_mcp	14s
typechecking for integrations/openai	13s
typechecking for integrations/langchain	11s
ruff check for integrations/dspy	11s
typechecking for integrations/llamaindex	11s
ruff check for integrations/llamaindex	9s
ruff check for .	19s
ruff check for integrations/langchain	12s
	2m 38s

Provide feedback