> The other part is the cohesive interface for the agent itself to use these selectors

We are incubating this over at the WebMCP web standard proposal. You can see the current draft of explainer for the declarative API. https://github.com/webmachinelearning/webmcp/pull/26

Also, great work on the browser agent, this is the best of the DOM parsing/screenshot agents I've used. I was really impressed with the wordle example