Function parse_react_step 

pub fn parse_react_step(response: &str) -> Result<ReActStep, AgentError>

Parses a raw LLM response string into a ReActStep.

Supported formats:

• Thought: <text>
• Action: <tool_name>(<input>)
• Action: <tool_name>: <input>
• Final Answer: <text>

Errors

Returns AgentError::ParseError if the response does not match any known prefix.