Add safer data access to run state internals in AsentsError classes

[eightHundreds]

Please read this first

• Have you read the docs? Agents SDK docs
• Have you searched for related issues? Others may have had similar requests

Describe the feature

What is the feature you're requesting? How would it work? Please provide examples and details if possible.

export abstract class AgentsError extends Error {
  state?: RunState<any, Agent<any, any>>;

  constructor(message: string, state?: RunState<any, Agent<any, any>>) {
    super(message);
    this.state = state;

+    this.name = new.target.name;
  }
}

// before
const a = new MaxTurnsExceededError();
console.log(a.name) // Error

//after
console.log(a.name)  // MaxTurnsExceededError

[seratch]

Thanks for the idea. It's feasible to access the current agent's name via error.state?._currentAgent but having to access underscored name is not great. Enhancing the data access is worth considering. We will think of robust design for it later.