Improve error reporting for process failures

Captures and displays standard error output when 'dotnet pack' or 'dotnet nuget push' commands fail, providing more detailed error information to the user.

aeqw89.tools.Publish/Program.cs

@@ -248,7 +248,8 @@ public static class Program {
                     e.ToString().EscapeMarkup()));
             }
         };
-        
+
+        string processError = "";
         var exitCode = AnsiConsole.Status()
             .Spinner(Spinner.Known.Dots)
             .Start<int>("Creating package with 'dotnet pack' ", ctx => {
@@ -261,10 +262,12 @@ public static class Program {
                     RedirectStandardError = !Verbose
                 });
                 p?.WaitForExit();
+                processError = p?.StandardError?.ReadToEnd() ?? "";
                 return p?.ExitCode ?? -1;
             });
 
         if (exitCode != 0) {
+            ShowError(processError.EscapeMarkup());
             ShowError(Exceptions.dotnet_pack_failure.EscapeMarkup(), exitCode);
             return;
         }
@@ -420,7 +423,9 @@ public static class Program {
                             task.Increment(size / 2);
                             if (p != null)
                                 await p.WaitForExitAsync(ct);
+                            processError += p?.StandardError?.ReadToEnd() ?? "";
                             if (p?.ExitCode != 0) {
+                                ShowError(processError.EscapeMarkup());
                                 ShowError(Exceptions.dotnet_nuget_push_failure, p.ExitCode);
                             }
                             task.Increment(size / 2);