fix: offline-content renamed to downloads

lib/offline.ts

@@ -9,7 +9,7 @@
  *   - **Transcript audio** → a Blob in IndexedDB, played through a pre-created
  *     object URL (full native seeking; see `primeOfflineAudio`).
  *
- * An `items` index (IndexedDB) records what's saved so `/offline-content` can
+ * An `items` index (IndexedDB) records what's saved so `/downloads` can
  * list it and the header button can show saved state.
  */
 
@@ -212,13 +212,13 @@ async function cachePageAndAssets(
   return { htmlLength: html.length, assetCount: assetUrls.length };
 }
 
-/** Precache the /offline-content library page so it works as the SW's offline
+/** Precache the /downloads library page so it works as the SW's offline
  *  navigation fallback even if the user never opened it online. Best-effort. */
 export async function precacheOfflineLibrary(): Promise<void> {
   if (!offlineSupported()) return;
   try {
     await cachePageAndAssets(
-      new URL("/offline-content", window.location.origin).href,
+      new URL("/downloads", window.location.origin).href,
     );
   } catch {
     /* best-effort */