High-resolution and free-spin wheels on Windows send fractions of a line
(e.g. 0.125 per event); rounding each one up turned a single notch into
several slides. The fractional line delta now accumulates in ui.data temp
state, resets when the direction changes, and each whole line is one
slide. slide.go is skipped when the target is the current slide.
Test: eight 0.125-line events turn exactly one slide, and a reversal
drops the leftover fraction.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>