Update bundled yt-dlp and report source failures in chat

The image shipped a year-old yt-dlp, which YouTube now rejects with
"The page needs to be reloaded". Bumped to 2026.08.19 and documented
rebuilding as the standard fix, including how to pass a newer tag
without waiting for a repository update.

A downloader dying mid-stream also looked exactly like a very short
track: ffmpeg saw EOF, the player advanced, and the channel only got
"queue finished". The failure reason now reaches the chat.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/player.ts

@@ -276,6 +276,14 @@ export class GuildPlayer extends EventEmitter<GuildPlayerEvents> {
       // stop() rebuilds the volume transformer, so volume is applied per track.
       media.setVolume(this.volume / 100);
       this.startTicker();
+
+      // A downloader that dies mid-stream just looks like a very short track, so
+      // say why instead of silently moving on.
+      void input.failure?.then((reason) => {
+        if (!reason || this.current?.id !== track.id) return;
+        this.log.warn({ reason, track: track.title }, "source failed while streaming");
+        this.notify(`⚠️ **${track.title}** — источник отдал ошибку: ${reason}`);
+      });
     } catch (err) {
       this.log.warn({ err, track: track.title }, "playback failed");
       const message = err instanceof UserFacingError ? err.message : "неизвестная ошибка";