docs: final review fixes — deferred backlog, doc accuracy, sample-data note

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/shared/audio-slot.ts

@@ -21,7 +21,7 @@ export function createAudioSlot(song: Song): HTMLElement {
     btn.textContent = part.name;
     btn.addEventListener("click", () => {
       audio.currentTime = part.startSec!;
-      void audio.play?.();
+      audio.play?.()?.catch(() => {});
     });
     root.append(btn);
   }