fix: PitchOverview playhead wraps correctly for shorter patterns

When a track had fewer steps than MAX_STEPS (128), the playhead
indicator in PitchOverview would stop highlighting after the first
loop through the track's stepCount. For example, a 64-step track
would show the playhead for steps 0-63, but nothing for steps 64-127.

Root cause: The playhead check used `currentStep === i` but currentStep
ranges 0-127 while the grid only has indices 0-63.

Fix: Changed to `(currentStep % maxStepCount) === i` to wrap the
global step position to the local grid size.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: adewale

app/src/components/PitchOverview.tsx

@@ -161,7 +161,7 @@ export const PitchOverview = memo(function PitchOverview({
               return (
                 <div
                   key={i}
-                  className={`pitch-bar-cell ${isBeatStart ? 'beat-start' : ''} ${isPageEnd ? 'page-end' : ''} ${isPlaying && currentStep === i ? 'playing' : ''} ${data.hasOutOfScale ? 'out-of-scale' : ''}`}
+                  className={`pitch-bar-cell ${isBeatStart ? 'beat-start' : ''} ${isPageEnd ? 'page-end' : ''} ${isPlaying && (currentStep % maxStepCount) === i ? 'playing' : ''} ${data.hasOutOfScale ? 'out-of-scale' : ''}`}
                   title={data.pitches.length > 0
                     ? `Step ${i + 1}: ${data.pitches.map(p => pitchToNoteName(p)).join(', ')}`
                     : `Step ${i + 1}: no notes`