Implemented tag refresh on a playlist. Made audio file scanning truly asynchronous. Added basic playlist sorting functionality.

Harmonia.Core/Scanner/AudioFileScanner.cs

@@ -9,22 +9,19 @@ public class AudioFileScanner(IAudioEngine audioEngine, ITagResolver tagResolver
 {
     public async Task<Song[]> GetSongsAsync(string[] fileNames, CancellationToken cancellationToken)
     {
-        List<Song> songs = [];
+        Song?[] songs = new Song?[fileNames.Length];
 
-        foreach (string fileName in fileNames)
+        await Parallel.ForEachAsync(Enumerable.Range(0, fileNames.Length), cancellationToken, async (index, token) =>
         {
+            string fileName = fileNames[index];
+
             if (string.IsNullOrWhiteSpace(fileName) || File.Exists(fileName) == false)
-                continue;
+                return;
 
-            Song? song = await GetSongAsync(fileName, cancellationToken);
+            songs[index] = await GetSongAsync(fileName, token);
+        });
 
-            if (song == null)
-                continue;
-
-            songs.Add(song);
-        }
-
-        return [.. songs];
+        return [.. songs.Where(song => song != null)!];
     }
 
     private async Task<Song> GetSongAsync(string fileName, CancellationToken cancellationToken)