fix: practice defense driving...seal it all

src/StreamShorts.Library/Media/Audio/AudioExtractor.cs

@@ -4,7 +4,7 @@ namespace StreamShorts.Library.Media.Audio;
 /// Extracts audio from video files.
 /// </summary>
 /// <inheritdoc/>
-public class AudioExtractor : IAudioExtractor
+public sealed class AudioExtractor : IAudioExtractor
 {
   private readonly IVideoService _videoService = new FFMpegService();
 

src/StreamShorts.Library/Media/Audio/FailedAudioExtractionException.cs

@@ -1,15 +1,30 @@
 namespace StreamShorts.Library.Media.Audio;
 
-public class FailedAudioExtractionException : Exception
+/// <summary>
+/// Represents an error that occurs when audio extraction fails.
+/// </summary>
+public sealed class FailedAudioExtractionException : Exception
 {
+  /// <summary>
+  /// Initializes a new instance of the <see cref="FailedAudioExtractionException"/> class.
+  /// </summary>
   public FailedAudioExtractionException() : base()
   {
   }
 
+  /// <summary>
+  /// Initializes a new instance of the <see cref="FailedAudioExtractionException"/> class with a specified error message.
+  /// </summary>
+  /// <param name="message">The error message that explains the reason for the exception.</param>
   public FailedAudioExtractionException(string message) : base(message)
   {
   }
 
+  /// <summary>
+  /// Initializes a new instance of the <see cref="FailedAudioExtractionException"/> class with a specified error message and a reference to the inner exception that is the cause of this exception.
+  /// </summary>
+  /// <param name="message">The error message that explains the reason for the exception.</param>
+  /// <param name="innerException">The exception that is the cause of the current exception.</param>
   public FailedAudioExtractionException(string message, Exception innerException) : base(message, innerException)
   {
   }

src/StreamShorts.Library/Media/FFMpegService.cs

@@ -10,7 +10,7 @@ namespace StreamShorts.Library.Media;
 /// Represents a service for processing video files using FFMpeg.
 /// </summary>
 /// <inheritdoc/>
-internal class FFMpegService : IVideoService
+internal sealed class FFMpegService : IVideoService
 {
   public async Task<bool> ExtractAudioFromVideoAsync(Stream video, Stream audio)
   {

src/StreamShorts.Library/Media/NAudioService.cs

@@ -7,7 +7,7 @@ namespace StreamShorts.Library.Media;
 /// Represents a service for processing audio files using NAudio.
 /// </summary>
 /// <inheritdoc/>
-internal class NAudioService : IAudioService
+internal sealed class NAudioService : IAudioService
 {
   public Stream ConvertMp3ToWav16(Stream mp3)
   {