agentic init: make sure to handle archived or outdated content

As part of @vhvb1989's work to make it more clear to customers when they're using an archived (ie, unmaintained) template, we should ensure we do sensible things in agentic init.

The simplest thing is to add some instructions to make sure it doesn't pick one of those, and possibly to search awesome-azd for supported templates and pick one of those. I often find it just _creates_ the project, however, so some of these instructions might just be "don't use this as an example, or if you do, keep in mind you should modernize it".