Creating an agent file manually gives me no affordance to fill it in

[TylerLeonhardt]

Creating an agent file manually gives me no affordance to fill it in

Steps:

• create a file .github/agents/foo.md
• see blank slate

I think we should have some affordance to pre-fill the front matter. Especially since some of the properties are required (maybe?)

[aeschli]

I don't know how I would hook in the 'new file created' flow.
However I added a code completion that shows up on empty content:

[sbatten]

We should really show a different "placeholder text" in the editor. Generate code and Select a language make no sense and we know what this file is for based on the path.