Whether a scene is well formed, or the first problem in it.

Checks a scene document with the engine's strict reader without rendering it: ok, or one sentence naming the first problem and the key it is at, with every other problem in the scene listed in result.errors (up to fifty), so one call finds them all. A scene with dialogue is spoken while it is read, so a long one takes a few seconds, and a line that overlaps the same character's last, or ends after the scene, is named. Costs no units.