UX on assigning issue to copilot

[eleanorjboyd]

for discoverability it would be cool if copilot was listed at the top of the "assign to" list so users knew this was an option. Also maybe somewhere clarify that adding it as an assignee will make the copilot-swe-agent begin working? (comes from testing #6832 and verifying related issues)

cc @kkbrooks and @hawkticehurst

[alexr00]

I don't want to break anyone's muscle memory by putting Copilot first. I already added a quick action for it:

However, I do think it makes sense to indicate that Copilot will start working on it if you assign it.

[alexr00]

To verify:

• Install the pre-release version of GitHub Pull Requests
• Open a clone of a GitHub repository where you can assign issues to Copilot
• Open an issue webview from the Issues view
• In the "Assignees" section, hover over the Copilot icon and verify that it says "Assign for Copilot to work on"