Microsoft.Agents.AI.AGUI naming is misleading since it does not implement AIAgent

[westey-m]

The naming for the Microsoft.Agents.AI.AGUI package is misleading, since similarly named packages provide AIAgent for remote agents. While Microsoft.Agents.AI.AGUI is also a client for a remote agent, it does not provide an AIAgent implementation, but rather just an IChatClient implementation.

We should make sure that it also consistently implements AIAgent, or rename the package to indicate that it is really providing an IChatClient implementation rather than an AIAgent implementation.