Better clarify when the tutorial expects exercising within the repo or in your own from scratch

[Cervator]

Had a GCI student note that while working in a new module from scratch (with a valid dependency on Core) no part of the tutorial seemed to indicate the need to create a House class - thus it was still missing and the examples didn't compile.

Probably that needs to be a step in the tutorial rather than anything awkward like making a dependency in a separate module on the TutorialWorldGeneration module. May also be good to do an overall review of where the tutorial guides the user to work (looking at how the tutorial repo itself works vs trying to start from scratch step by step)