fix(reader): clean up focus mode footer

- Hide the global site footer on chapter pages (not useful mid-reading)
- Merge the three separate floating nav pills into a single unified pill
  with dividers, removing the visual clutter of multiple bordered bubbles
- Float the pill lower (bottom-6) when the mini-player is not active

ui/src/routes/+layout.svelte

@@ -721,7 +721,9 @@
 		{/key}
 	</main>
 
-	<footer class="border-t border-(--color-border) mt-auto">
+	<footer class="border-t border-(--color-border) mt-auto"
+		class:hidden={/\/books\/[^/]+\/chapters\//.test(page.url.pathname)}
+	>
 		<div class="max-w-6xl mx-auto px-4 py-6 flex flex-col items-center gap-4 text-xs text-(--color-muted)">
 			<!-- Top row: site links -->
 			<nav class="flex flex-wrap items-center justify-center gap-x-5 gap-y-2">