Opening this issue to decide on a name for the main object going forward.

The current API proposal uses window.agent. window.mcp has been proposed elsewhere and I'd like to suggest switching to this.

agent (singular) may not be the best choice of name since it assumes there's only one agent. Support for multiple different agent clients has come up recently in issues like #20, #16. Even a single agent product (i.e. Claude, Copilot, Gemini) can have multiple different conversations which can be thought of as unique clients from the page's point of view. So agent seems less appropriate than it did when first drafting the explainer.