[Feature Request] Add a `Reason` when rejecting a puzzle

Since we can have multiple people reviewing puzzles, it would be useful to know why a puzzle was rejected when that happens, so others can see the reason and maybe edit the puzzle and move it back to pending for example?

No file, test, or entry point is named. Start by locating the puzzle rejection flow and the place where puzzle status or review information is displayed; determine how a rejection reason would be stored, shown to other reviewers, and support returning a puzzle to pending. Done means reviewers can see the reason for a rejection.

Written by the indexing model from the issue text.