CLI middleware for runtime model selection via LangGraph runtime context.
Allows switching the model per invocation by passing a CLIContext via
context= on agent.astream() / agent.invoke() without recompiling
the graph.
Runtime context passed via context= to the LangGraph graph.
Carries per-invocation overrides that ConfigurableModelMiddleware
reads from request.runtime.context.
Swap the model or per-call settings from runtime.context.
