Address review feedback: add CI env var check and return non-zero exit code

- CertCommand and ProxyEngine: check both Console.IsInputRedirected and
  CI env var for non-interactive detection, matching ExecuteAsync pattern
- RemoveCert returns int: exit code 1 for non-interactive failure or
  exceptions, 0 for success

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

Author: Copilot

DevProxy/Commands/CertCommand.cs

@@ -74,7 +74,7 @@ private async Task EnsureCertAsync()
         _logger.LogTrace("EnsureCertAsync() finished");
     }
 
-    public void RemoveCert(ParseResult parseResult)
+    public int RemoveCert(ParseResult parseResult)
     {
         _logger.LogTrace("RemoveCert() called");
 
@@ -83,16 +83,17 @@ public void RemoveCert(ParseResult parseResult)
             var isForced = parseResult.GetValue(_forceOption);
             if (!isForced)
             {
-                if (Console.IsInputRedirected)
+                if (Console.IsInputRedirected ||
+                    Environment.GetEnvironmentVariable("CI") is not null)
                 {
                     _logger.LogError("Confirmation required but running in non-interactive mode. Use --force to skip confirmation.");
-                    return;
+                    return 1;
                 }
 
                 var isConfirmed = PromptConfirmation("Do you want to remove the root certificate", acceptByDefault: false);
                 if (!isConfirmed)
                 {
-                    return;
+                    return 0;
                 }
             }
 
@@ -117,10 +118,12 @@ public void RemoveCert(ParseResult parseResult)
             }
 
             _logger.LogInformation("DONE");
+            return 0;
         }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Error removing certificate");
+            return 1;
         }
         finally
         {

DevProxy/Proxy/ProxyEngine.cs

@@ -233,7 +233,8 @@ private void FirstRunSetup()
         Console.WriteLine("Dev Proxy uses a self-signed certificate to intercept and inspect HTTPS traffic.");
 
         string? answer;
-        if (Console.IsInputRedirected)
+        if (Console.IsInputRedirected ||
+            Environment.GetEnvironmentVariable("CI") is not null)
         {
             // Non-interactive mode, default to trusting the certificate
             _logger.LogInformation("Non-interactive mode detected. Defaulting to trusting the certificate.");