chapter page: show book title in nav header, simplify back button and heading

ui/src/routes/+layout.svelte

@@ -211,10 +211,16 @@
 	{/if}
 	<header class="border-b border-zinc-700 bg-zinc-900 sticky top-0 z-50">
 		<nav class="max-w-6xl mx-auto px-4 h-14 flex items-center gap-6">
-			<a href="/" class="text-amber-400 font-bold text-lg tracking-tight hover:text-amber-300">
+			<a href="/" class="text-amber-400 font-bold text-lg tracking-tight hover:text-amber-300 shrink-0">
 				libnovel
 			</a>
 
+			{#if page.data.book?.title && /\/books\/[^/]+\/chapters\//.test(page.url.pathname)}
+				<span class="text-zinc-400 text-sm truncate min-w-0 flex-1 sm:flex-none sm:max-w-xs">
+					{page.data.book.title}
+				</span>
+			{/if}
+
 			{#if data.user}
 				<!-- Desktop nav links (hidden on mobile) -->
 				<a

ui/src/routes/books/[slug]/chapters/[n]/+page.svelte

@@ -68,7 +68,7 @@
 		<svg class="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
 			<path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M15 19l-7-7 7-7" />
 		</svg>
-		{data.book.title}
+		Chapters
 	</a>
 
 	<div class="flex gap-2">
@@ -93,7 +93,6 @@
 
 <!-- Chapter heading -->
 <div class="mb-6">
-	<p class="text-zinc-500 text-sm mb-1">Chapter {data.chapter.number}</p>
 	<h1 class="text-xl font-bold text-zinc-100">
 		{data.chapter.title || `Chapter ${data.chapter.number}`}
 	</h1>