toForwardedProps

An action the user took on a surface, in the shape upstream's middleware reads it from RunAgentInput.forwardedProps: {"a2uiAction": {"userAction": {...}}}.

The middleware lifts it into a synthetic assistant tool call named log_a2ui_event plus its result, so the model sees the action as something that happened in the conversation. The five fields are the A2UI action message's own, which is why this is a rename and not a mapping. Merge it into whatever else the run forwards; this module does not own forwardedProps.