Call a Golem tool from MoonBit

#derive.tool generates <Tool>Client in golem_tool_clients.mbt:

async fn call_echo() -> Result[String, @tool.ToolError[@tool.NoToolError]] {
  let client = EchoClient::new()
  defer client.drop()
  client.echo("hello")
}

Call generated tool methods from an async fn; MoonBit has no await keyword. Use new_for(name) when targeting another registration name. Generated signatures preserve custom errors and stream capabilities; handle the returned @tool.ToolError[E] rather than assuming every failure is a domain error. Always call drop() when finished, and never edit the generated client.