Reify minimum viable scene structure

[mkremins]

From the “StoryAssembler as a standalone library” perspective (like @Logodaedalus and I were discussing earlier), a “scene” (right now) basically consists of the following:

• An ID string
• A chunk library
• A wishlist
• An initial blackboard state
• Maybe a cast of characters (although right now we’re basically only using these to store more variable/value pairs, so we could probably merge this into the initial state)

Ideally, then, we should be able to reify this structure by representing each scene as a single JSON object with these properties.