Currently, web-nodekit only supports downloading text files. To save a canvas snap shot I added a bit of javacript inject code. You can download it here: http://wiki.goalorientedsolutions.com/d ... pshot_file
Please be aware that due to some current discrepancies between web-nodekit in the preview and when exported, the save feature only works projects exported to web-nodekit.
p.s. thanks to emoaeden for encouraging me to package this in a capx.