fix(reader): clean chapter title display and declutter audio panel

- Strip leading digit prefix (e.g. "6Chapter 6 → Chapter 6") and
  content after first newline (scraped date artifacts) from chapter titles
- Add "CHAPTER N" eyebrow label above the h1 for clear hierarchy
- Show date_label as small muted text in the meta row
- Remove double-border / mt-6 gap from standard AudioPlayer inside the
  chapter page's collapsible panel (was rendering two nested boxes)
- Remove redundant "Audio Narration" label (toggle already says "Listen")

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/lib/components/AudioPlayer.svelte

@@ -1024,15 +1024,8 @@
 </div>
 {:else}
 <!-- ── Standard player ─────────────────────────────────────────────────────── -->
-<div class="mt-6 p-4 rounded-lg bg-(--color-surface-2) border border-(--color-border)">
-	<div class="flex items-center justify-between gap-2 mb-3">
-		<div class="flex items-center gap-2">
-			<svg class="w-4 h-4 text-(--color-brand)" fill="currentColor" viewBox="0 0 24 24">
-				<path d="M12 3v10.55A4 4 0 1014 17V7h4V3h-6z"/>
-			</svg>
-			<span class="text-sm text-(--color-text) font-medium">{m.reader_audio_narration()}</span>
-		</div>
-
+<div class="p-4">
+	<div class="flex items-center justify-end gap-2 mb-3">
 		<!-- Voice selector button -->
 		{#if voices.length > 0}
 			<Button