YT: audio presets no longer pass --merge-output-format (it swallowed -o and broke every audio download)

ddiff --git a/apps/yt/server/downloader.js b/apps/yt/server/downloader.js
iindex 616b448..7c116cb 100644
---- a/apps/yt/server/downloader.js
++++ b/apps/yt/server/downloader.js
@@@ -186,9 +186,13 @@ function startDownload(url, quality = 'best') {
          ensureDir();
          const outputTemplate = path.resolve(config.downloadsDir, `${id}.%(ext)s`);
  
--        const args = [
++        // Audio presets must not get --merge-output-format at all: the old '' placeholder was
++        // dropped by filter(Boolean) before the cleanup loop ran, so yt-dlp received
++        // `--merge-output-format -o` and every audio download died with
++        // "invalid merge output format "-o" given".
++        const cleanArgs = [
              '-f', preset.video,
--            '--merge-output-format', preset.audio ? '' : (preset.ext || 'mp4'),
++            ...(preset.audio ? [] : ['--merge-output-format', preset.ext || 'mp4']),
              '-o', outputTemplate,
              '--no-playlist',
              '--no-warnings',
@@@ -196,14 +200,7 @@ function startDownload(url, quality = 'best') {
              '--progress-template', '%(progress._percent_str)s %(progress._speed_str)s %(progress._eta_str)s',
              ...(preset.postprocess || []),
              cleanUrl,
--        ].filter(Boolean);
--
--        // Remove empty merge-output-format for audio
--        const cleanArgs = [];
--        for (let i = 0; i < args.length; i++) {
--            if (args[i] === '--merge-output-format' && args[i + 1] === '') { i++; continue; }
--            cleanArgs.push(args[i]);
--        }
++        ];
  
          const entry = {
              id,