Every pedal-down must be matched by a later pedal-up before the next pedal-down or the piece's end

A `Ped.` (pedal down) mark must be released with a `✱` (pedal up) mark before a new pedal-down begins, and every pedal engaged must eventually be released.

A `ScoreNote` sets `pedalDown: true` at beat 4 of measure 10, and the next pedal-related event in that instrument's part is ANOTHER `pedalDown: true` at measure 12 with no `pedalUp: true` anywhere between them — the first pedal is never released.

Gould, Behind Bars, ch. Pedalling — pedal marks always come in matched down/up pairs.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.