Function update_tool_message 

pub fn update_tool_message(
    conn: &Connection,
    session_id: &str,
    tool_call_id: &str,
    content: &str,
    tool_info: &str,
) -> Result<()>

Update a tool message with its result.

content replaces the message content (initially the call arguments, replaced by the actual tool output once available) so that restored history carries the real result. tool_info is the UI-facing JSON state.