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

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/shared.test.ts

@@ -48,6 +48,18 @@ describe("createAudioSlot", () => {
     expect(el.querySelectorAll("audio[src]")).toHaveLength(1);
     expect(el.querySelectorAll('button[data-start="30"]')).toHaveLength(1);
   });
+  test("seek button sets currentTime and swallows a rejected play()", async () => {
+    const { createAudioSlot } = await import("../src/shared/audio-slot");
+    const song: Song = { ...base, audio: "/a.mp3", parts: [{ ...base.parts[0]!, startSec: 30 }] };
+    const el = createAudioSlot(song);
+    const audio = el.querySelector("audio") as HTMLAudioElement;
+    let played = 0;
+    audio.play = () => { played++; return Promise.reject(new Error("blocked")); };
+    (el.querySelector("button.audio-slot__seek") as HTMLButtonElement).click();
+    await Promise.resolve();
+    expect(audio.currentTime).toBe(30);
+    expect(played).toBe(1);
+  });
 });
 
 describe("createVideoCards", () => {