My web application has a 'code view' (an embedded IDE) and a visual/parsed view with forms/buttons etc.
What should I call this second view?
That's really what it is. You're doing your best to show them what the final product in the final renderer will look like.
There is an important implication behind this word choice. "Preview" tells the user that you're giving them a peek at the final product, but it doesn't sound quite as set-in-stone as "Live" or other such terms.
I've generally seen this referred to as a "Live" view.
e.g. Adobe Dreamweaver has 'Code' 'Split' and 'Live' views.
'Live' in this case means just what you've described in your question - "a visual/parsed view".