fix: align automation lane with waveform, improve header layout

Automation lane improvements:
- Lane now aligns exactly with waveform width using two-column layout
- Added 180px left spacer to match track controls sidebar
- Playhead marker now aligns perfectly with waveform

Automation header improvements:
- Dropdown has fixed width (min-w-[120px] max-w-[200px]) instead of flex-1
- Eye icon (show/hide) is now positioned absolutely on the right
- Cleaner, more compact header layout

Visual consistency:
- Removed redundant border-b from AutomationLane (handled by parent)
- Automation lane and waveform now perfectly aligned vertically

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

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

components/automation/AutomationHeader.tsx

@@ -69,7 +69,7 @@ export function AutomationHeader({
   return (
     <div
       className={cn(
-        'flex items-center gap-2 px-2 py-1 bg-muted/50 border-b border-border/30 flex-shrink-0',
+        'relative flex items-center gap-2 px-2 py-1 bg-muted/50 border-b border-border/30 flex-shrink-0',
         className
       )}
     >
@@ -86,7 +86,7 @@ export function AutomationHeader({
         <select
           value={selectedParameterId}
           onChange={(e) => onParameterChange?.(e.target.value)}
-          className="text-xs font-medium text-foreground flex-1 min-w-0 bg-background/50 border border-border/30 rounded px-1.5 py-0.5 hover:bg-background/80 focus:outline-none focus:ring-1 focus:ring-primary"
+          className="text-xs font-medium text-foreground w-auto min-w-[120px] max-w-[200px] bg-background/50 border border-border/30 rounded px-1.5 py-0.5 hover:bg-background/80 focus:outline-none focus:ring-1 focus:ring-primary"
         >
           {availableParameters.map((param) => (
             <option key={param.id} value={param.id}>
@@ -95,7 +95,7 @@ export function AutomationHeader({
           ))}
         </select>
       ) : (
-        <span className="text-xs font-medium text-foreground flex-1 min-w-0 truncate">
+        <span className="text-xs font-medium text-foreground truncate">
           {parameterName}
         </span>
       )}
@@ -142,13 +142,13 @@ export function AutomationHeader({
         </div>
       )}
 
-      {/* Show/hide toggle */}
+      {/* Show/hide toggle - Positioned absolutely on the right */}
       <Button
         variant="ghost"
         size="icon-sm"
         onClick={onToggleVisible}
         title={visible ? 'Hide automation' : 'Show automation'}
-        className="h-5 w-5 flex-shrink-0"
+        className="absolute right-2 h-5 w-5 flex-shrink-0"
       >
         {visible ? (
           <Eye className="h-3 w-3" />