fix(web): drop the shelf-header accent rule Tailwind 4 started drawing (#5021)

The rule after each shelf title used `after:bg-accent/60`. Tailwind 3
cannot put an opacity modifier on a `var()` colour, so it emitted nothing
for that class and the rule never showed. Tailwind 4 mixes the opacity
in with color-mix, so the rule appeared after the upgrade. Removed, so
the headers look as they did before.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/lib/components/HorizontalScrollRow.svelte

@@ -62,14 +62,8 @@
 <div class="section" aria-label={ariaLabel}>
   <header class="section-header">
     {#if title}
-      <!-- Section header: Fraunces (font-display) at 24px with an
-           inline accent rule that bleeds out from the title — gives
-           each shelf a clear chapter break without adding chrome. -->
-      <h2
-        class="font-display text-2xl font-medium text-text-primary
-               flex items-baseline gap-3 after:h-[2px] after:w-12 after:shrink-0
-               after:rounded-full after:bg-accent/60 after:content-['']"
-      >{title}</h2>
+      <!-- Section header: Fraunces (font-display) at 24px. -->
+      <h2 class="font-display text-2xl font-medium text-text-primary">{title}</h2>
     {:else}
       <span></span>
     {/if}