The per-voice beat-total sanity check must still run — correctly — when tuplets are present, not be skipped

A tuplet changes a group of notes' sounding duration relative to their written duration, but the correct check is: sounding duration (written duration × notes_occupied/num_notes for each tupleted note) must still sum, across the whole voice, to a whole multiple of the bar length. Tuplets are exactly the case where beat-arithmetic verification is MOST needed, not a case to abstain from.

Follows directly from standard duration arithmetic (Gould, Behind Bars, ch. 'Tuplets'; Read, Music Notation, tuplet duration chapter) — no notational authority exempts tupleted passages from bar-length arithmetic.

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