fix(baoyu-fetch): parse YouTube /embed/ URLs in parseYouTubeVideoId

parseYouTubeVideoId handled watch, youtu.be, /shorts/ and /live/ URLs but
not the common /embed/<id> player form, so embed links returned null and the
YouTube adapter treated them as "no document". Add an /embed/ branch
mirroring the existing /shorts/ and /live/ handling, with a regression test.

packages/baoyu-fetch/src/__tests__/youtube-utils.test.ts

@@ -19,6 +19,10 @@ describe("parseYouTubeVideoId", () => {
   test("parses shorts URLs", () => {
     expect(parseYouTubeVideoId(new URL("https://www.youtube.com/shorts/abc123"))).toBe("abc123");
   });
+
+  test("parses embed URLs", () => {
+    expect(parseYouTubeVideoId(new URL("https://www.youtube.com/embed/abc123"))).toBe("abc123");
+  });
 });
 
 describe("parseYouTubeDescriptionChapters", () => {

packages/baoyu-fetch/src/adapters/youtube/utils.ts

@@ -52,6 +52,11 @@ export function parseYouTubeVideoId(url: URL): string | null {
     return liveMatch[1];
   }
 
+  const embedMatch = url.pathname.match(/^\/embed\/([^/?#]+)/);
+  if (embedMatch) {
+    return embedMatch[1];
+  }
+
   return null;
 }