Initiate Padawan from the issues view (was Unexpected behavior of `->` and stop button in issues)

[bamurtaugh]

In the GHPRI issues view, I was exploring issues I created, and I was confused why one of them had a checkmark and a stop button:

I assumed this meant that the Copilot Coding Agent was working on the issue (and I could stop it if I'd like), but I realize it instead means that I've selected -> and assigned myself to the issue.

Some thoughts:

• Why would I want to use -> versus just clicking on the issue? Both paths bring the issue into focus. Is the main difference that -> assigns me to the issue?
• I'd like to use the stop button to instead indicate that the agent is working on an issue

[alexr00]

-> is how you initiate the "start working on an issue" flow. It creates and checks out a new branch for you. The stop button is how you "stop working on an issue" and will checkout your default branch again.

We should avoid re-purposing these icons in the issues view as it will break uses flow. For Padawan, we should find new icons if we want to support this from the issues view.

[alexr00]

We should add a right click context menu action to assign the issue to the coding agent.