fix: increase tickDenominator to 60480 for correct tuplet resolution

[KelvinCreighton]

Problem

The previous tickDenominator of 1024 (2^10) only guaranteed clean division
for regular notes. Tuplets such as triplets, quintuplets, and septuplets
produce RealValue denominators that don't divide evenly into 1024, causing
floating point tick positions and scheduling drift most noticeably with
16th note triplets and other edge cases.

Fix

Changed tickDenominator from 1024 to 60480.

60480 = 2^6 × 3^3 × 5 × 7

• 2^6 = 64: supports regular notes down to 64th notes
• 3^3 = 27: supports triplets, including triple-nested triplets
• 5: supports quintuplets
• 7: supports septuplets

This ensures all common tuplet RealValues divide evenly into the tick
grid, eliminating rounding errors in tick position calculation.

Trade-off

2^6 vs the previous 2^10 means lower binary resolution, but 64th note
precision is more than sufficient for any practical score.