refactor(SliderArea): remove $derived className

src/widgets/ComparisonView/ui/SliderArea/SliderArea.svelte

@@ -266,22 +266,6 @@ $effect(() => {
         cancelled = true;
     };
 });
-
-// Dynamic backgroundSize based on isMobile — can't express this in Tailwind.
-// Color is set to currentColor so it respects dark mode via text color.
-const gridStyle = $derived(
-    `background-image: linear-gradient(currentColor 1px, transparent 1px), linear-gradient(90deg, currentColor 1px, transparent 1px); `
-        + `background-size: ${isMobile ? '10px 10px' : '20px 20px'};`,
-);
-
-// When the sidebar opens on desktop, the canvas pads in on every side
-// so the paper insets evenly (equal pixel gaps top/bottom/left/right)
-// instead of shrinking proportionally with a transform — which on wide
-// viewports produced uneven horizontal vs. vertical gaps and also
-// caused the layout engine to measure the un-scaled width.
-const paddingClass = $derived(
-    isSidebarOpen && !isMobile ? 'p-6' : 'p-0',
-);
 </script>
 
 <!--
@@ -292,7 +276,7 @@ const paddingClass = $derived(
     class={cn(
         'flex-1 relative flex-center overflow-hidden surface-canvas',
         'transition-[padding] duration-slow ease-out',
-        paddingClass,
+        isSidebarOpen && !isMobile ? 'p-6' : 'p-0',
         className,
     )}
 >