I'll add some more documentation. When I say Dart SDK, what I'm actually referring to are the dart: libraries from the dart sdk (dart-sdk/lib). Having the sdk available to the app will be necessary for:
 * dart2js to compile against (otherwise it won't know anything about say dart:core String)
 * the analyzer to analyze against, so we can get warnings about incorrect API usage
 * the user to navigate to when doing things like exploring the dart apis

Also happy to rename things or move things around as necessary for clarity.