fix: hero carousel — horizontal book spine stack instead of vertical overlap

ui/src/routes/+page.svelte

@@ -136,12 +136,18 @@
 
 <!-- ── Hero carousel ──────────────────────────────────────────────────────────── -->
 {#if heroBook}
+{@const stackBooks = heroBooks.length > 1
+	? Array.from({ length: Math.min(heroBooks.length - 1, 3) }, (_, i) =>
+		heroBooks[(heroIndex + 1 + i) % heroBooks.length])
+	: []}
 <section class="mb-6">
-	<div class="relative">
-		<!-- Card — swipe to navigate -->
+	<!-- Outer flex row: front card + queued book spines (sm+ only) -->
+	<div class="relative flex items-stretch gap-0">
+
+		<!-- Front card — swipe to navigate -->
 		<!-- svelte-ignore a11y_no_static_element_interactions -->
 		<div
-			class="group relative flex gap-0 rounded-xl overflow-hidden bg-(--color-surface-2) border border-(--color-border) hover:border-(--color-brand)/50 transition-all"
+			class="group relative flex gap-0 rounded-xl overflow-hidden bg-(--color-surface-2) border border-(--color-border) hover:border-(--color-brand)/50 transition-all z-[2] flex-1 min-w-0"
 			ontouchstart={onSwipeStart}
 			ontouchend={onSwipeEnd}
 		>
@@ -198,23 +204,43 @@
 			</div>
 		</div>
 
-		<!-- Dot indicators -->
-		{#if heroBooks.length > 1}
-			<div class="flex items-center justify-center gap-2 mt-2.5">
-				{#each heroBooks as _, i}
-					<button
-						type="button"
-						onclick={() => heroDot(i)}
-						aria-label="Go to book {i + 1}"
-					>
-						<span class="block rounded-full transition-all duration-300 {i === heroIndex
-							? 'w-4 h-1.5 bg-(--color-brand)'
-							: 'w-1.5 h-1.5 bg-(--color-border) hover:bg-(--color-muted)'}"></span>
-					</button>
-				{/each}
-			</div>
-		{/if}
+		<!-- Queued book spines — visible sm+ only, peek to the right of the front card -->
+		{#each stackBooks as stackBook, i}
+			{@const opacity = i === 0 ? 'opacity-70' : 'opacity-40'}
+			{@const width = i === 0 ? 'sm:w-10' : 'sm:w-7'}
+			<a
+				href="/books/{stackBook.book.slug}/chapters/{stackBook.chapter}"
+				class="hidden sm:block shrink-0 {width} rounded-r-xl overflow-hidden border border-l-0 border-(--color-border) {opacity} hover:opacity-90 transition-opacity"
+				aria-label={stackBook.book.title}
+				tabindex="-1"
+			>
+				{#if stackBook.book.cover}
+					<img src={stackBook.book.cover} alt="" aria-hidden="true"
+						class="w-full h-full object-cover object-left" loading="lazy" />
+				{:else}
+					<div class="w-full h-full bg-(--color-surface-3)"></div>
+				{/if}
+			</a>
+		{/each}
+
 	</div>
+
+	<!-- Dot indicators -->
+	{#if heroBooks.length > 1}
+		<div class="flex items-center justify-center gap-2 mt-2.5">
+			{#each heroBooks as _, i}
+				<button
+					type="button"
+					onclick={() => heroDot(i)}
+					aria-label="Go to book {i + 1}"
+				>
+					<span class="block rounded-full transition-all duration-300 {i === heroIndex
+						? 'w-4 h-1.5 bg-(--color-brand)'
+						: 'w-1.5 h-1.5 bg-(--color-border) hover:bg-(--color-muted)'}"></span>
+				</button>
+			{/each}
+		</div>
+	{/if}
 </section>
 {/if}