Fix rep-volume scaling: only vary reps among same-movement levels

Previous commit wrongly rescaled reps on every level, including ones already
differentiated by a movement sub. Correct rule: a level's reps only change if it
performs the same movement as Rx; subbed levels keep the base count. So Toes-to-Bar
is 12/11/10 across the top three then base 10 on the leg-raise levels, while wall
ball (same movement throughout) scales 14..7. Barbell/KB untouched as before.

Author: OneMuppet