Agents window PR form: Expect link to PR to be provided

Testing #335496

After using `Create PR` to create a PR on my repo, I don't get any link in-product to that PR. I can go to my repo myself in the browser to verify it was created, but I expected to get some sort of link and notice in the chat output (like a message from the agent that prints out the PR) or header area (where I now see `Mark Ready` or `Merge` depending on if it's a draft PR).