DriveDiscovery: Add missing using System (for StringComparison)

FastSeekWpf/Core/DriveDiscovery.cs

@@ -16,6 +16,7 @@ public static class DriveDiscovery
         uint len = Win32Api.GetLogicalDriveStringsW((uint)buffer.Length, buffer);
         if (len == 0) return drives;
 
+        // Parse null-separated drive strings (same as Rust buf[..len].split(|&c| c == 0))
         var driveStrings = new List<string>();
         var sb = new StringBuilder();
         for (int i = 0; i < len; i++)