Fix OutputChannelObserver to suppress verbose error details for user-friendly exit codes

Co-authored-by: nagilson <[email protected]>

Author: Copilot

vscode-dotnet-runtime-library/src/EventStream/OutputChannelObserver.ts

@@ -14,6 +14,7 @@ import
     DotnetDebuggingMessage,
     DotnetExistingPathResolutionCompleted,
     DotnetInstallExpectedAbort,
+    DotnetNonZeroInstallerExitCodeError,
     DotnetOfflineInstallUsed,
     DotnetOfflineWarning,
     DotnetUpgradedEvent,
@@ -22,6 +23,7 @@ import
 import { EventType } from './EventType';
 import { IEvent } from './IEvent';
 import { IEventStreamObserver } from './IEventStreamObserver';
+import { WinMacGlobalInstaller } from '../Acquisition/WinMacGlobalInstaller';
 
 export class OutputChannelObserver implements IEventStreamObserver
 {
@@ -115,7 +117,37 @@ export class OutputChannelObserver implements IEventStreamObserver
                 if (this.inProgressDownloads.includes(error?.install?.installId ?? ''))
                 {
                     this.outputChannel.appendLine(`Failed to download .NET ${error?.install?.installId}:`);
-                    this.outputChannel.appendLine(error?.error?.message);
+                    
+                    // For user-friendly installer exit codes, show only the clean interpreted message
+                    if (error instanceof DotnetNonZeroInstallerExitCodeError)
+                    {
+                        const errorMessage = error?.error?.message || '';
+                        const exitCodeMatch = errorMessage.match(/The exit code it gave us: (\w+)\./);
+                        if (exitCodeMatch && WinMacGlobalInstaller.IsUserFriendlyExitCode(exitCodeMatch[1]))
+                        {
+                            // Extract just the interpreted message (everything after the exit code line)
+                            const lines = errorMessage.split('\n');
+                            if (lines.length > 1)
+                            {
+                                this.outputChannel.appendLine(lines.slice(1).join('\n'));
+                            }
+                            else
+                            {
+                                this.outputChannel.appendLine(errorMessage);
+                            }
+                        }
+                        else
+                        {
+                            // Show full error message for non-user-friendly codes
+                            this.outputChannel.appendLine(error?.error?.message);
+                        }
+                    }
+                    else
+                    {
+                        // Show full error message for non-installer errors
+                        this.outputChannel.appendLine(error?.error?.message);
+                    }
+                    
                     this.outputChannel.appendLine('');
 
                     this.updateDownloadIndicators(error.install?.installId);