Check all callouts etc are correct type

### How could the content be improved?

Per #1605 some of the callouts (and/or testimonials, challenges, and other special page sections using the `:::::` syntax) were originally set to types based primarily on visual aspects (color, etc.) and may not match their actual purpose. When possible, it would be good to go through each episode and check that these sections are correctly typed and consistently structured.

Start by reading #1605 for the intended callout types and then inspect each episode for sections using the `:::::` syntax, including callouts, testimonials, and challenges. Done means these sections use types that match their purpose and are structured consistently across the episodes.

Written by the indexing model from the issue text.