Quiet Avalonia log sink to Fatal-only (suppress WSL/Linux noise)

GLX blacklist and DBus connection errors are non-fatal on WSL/Linux
but printed to stderr at Error level, alarming users. Raise sink
threshold to Fatal so only actual crashes produce console output.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bammf1

Program.cs

@@ -139,7 +139,7 @@ public static AppBuilder BuildAvaloniaApp()
 internal sealed class StderrLogSink : Avalonia.Logging.ILogSink
 {
     public bool IsEnabled(Avalonia.Logging.LogEventLevel level, string area)
-        => level >= Avalonia.Logging.LogEventLevel.Error;
+        => level >= Avalonia.Logging.LogEventLevel.Fatal;
 
     public void Log(Avalonia.Logging.LogEventLevel level, string area, object? source, string messageTemplate)
     {