Add interactions sandbox screens to screenshot tests

[zsoltk]

All current sandbox screens should be added to screenshot tests to make sure we don't break them.

Just the baseline would do fine (i.e. no scenarios are needed at this point). Yesterday I broke Puzzle15 with #539 , fixing in #544, but could've caught it easily:

To be clear, this issue is not about puzzle15, just an example of what broke. All other samples should be covered too.