[These are not highest priority, but are so easy that they are worth
not delaying until after bigger features below.]
-• Fix /puzzle dialog to reject a puzzle with the same URL as an
- existing puzzle.
-
• Make /solved clear the state string for a puzzle.
Round management
----------------
-• Add a /round command to create a new round. This is like a puzzle in
- that it has its own channel, but different in that it doesn't accept
- a solution, etc.
+• Group the puzzles in the Turbot home view by round
-• Add an (optional) drop-down at puzzle creation for selecting a known
- round for a puzzle, (or creating a new round). Ensure this mechanism
- allows for puzzles to exist in multiple rounds.
+• Select round fields by default based on the round of the puzzle for
+ the channel in which `/puzzle` is invoked.
• Consider putting a round prefix into the channel name to group a
round's puzzles in the channel list.