AIAgentRewindToUserMessage Method

Rewinds the conversation to just before the user turn at userMessageIndex (0-based, counting only user messages). Removes that user message and every message that followed it — including the assistant replies, tool calls and tool results — so the conversation returns to the state it had before that message was sent. Returns the text of the removed user message (so the caller can re-populate the input box), or null when the index is out of range.

public string RewindToUserMessage(
	int userMessageIndex
)