fix: restore horizontal scrollbar by making waveform use container height

- Remove fixed height from Track waveformOnly mode
- Use h-full class to fill flex container instead
- Allows parent scroll container to show horizontal scrollbar based on zoom
- Waveform now properly expands horizontally without clipping

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

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

components/tracks/Track.tsx

@@ -830,10 +830,9 @@ export function Track({
     return (
       <div
         className={cn(
-          "relative bg-waveform-bg border-b transition-all duration-200",
+          "relative bg-waveform-bg border-b transition-all duration-200 h-full",
           isSelected && "bg-primary/5",
         )}
-        style={{ height: trackHeight }}
       >
         {/* Inner container with dynamic width */}
         <div

components/tracks/TrackList.tsx

@@ -208,13 +208,13 @@ export function TrackList({
               <React.Fragment key={track.id}>
                 {/* Track Waveform Row with bars stacked below - Fixed height container */}
                 <div
-                  className="flex flex-col overflow-hidden"
+                  className="flex flex-col"
                   style={{
                     height: track.collapsed ? '48px' : `${track.height || 240}px`
                   }}
                 >
                   {/* Waveform - Takes remaining space */}
-                  <div className="flex-1 min-h-0">
+                  <div className="flex-1 min-h-0 relative">
                     <Track
                     track={track}
                     zoom={zoom}