Clarify rules around timer starting/stopping

docs/leaderboards/rules.md

@@ -12,10 +12,15 @@ These rules may be flexible, especially for new categories. For example, if you'
 
 - [These programs](/software/index.md#what-program-should-i-download) are recommended for speedsolving. If using a program not listed here, you should ask on the Discord first.
 - The puzzle must be solved from a full scramble.
+    - No twists may be applied between the puzzle being scrambled and the timer starting, or else the solve counts as a [DNF]. Full-puzzle rotations, including gyros, are allowed.
+    - When the timer is stopped the puzzle must be solved, or else the solve counts as a [DNF].
+    - Twists may be applied after the timer is stopped, but these moves are discounted.
 - Spectators may commentate, but must not help the solver.
 - Algorithm reference sheets are strongly discouraged.[^algsheets]
 - Reversing the scramble is not allowed; the solution must be novel.
 
+[DNF]: https://en.wikipedia.org/wiki/Did_not_finish
+
 ## Speedsolving rules
 
 These rules apply generally to speedsolving submissions unless the category has specific rules.