Fix .NET CLI server mode code samples to include UseStdio = false

Co-authored-by: friggeri <106686+friggeri@users.noreply.github.com>

Author: Copilot

docs/getting-started.md

@@ -1033,7 +1033,8 @@ using GitHub.Copilot.SDK;
 
 using var client = new CopilotClient(new CopilotClientOptions
 {
-    CliUrl = "localhost:4321"
+    CliUrl = "localhost:4321",
+    UseStdio = false
 });
 
 // Use the client normally

dotnet/src/Client.cs

@@ -70,7 +70,7 @@ public partial class CopilotClient : IDisposable, IAsyncDisposable
     /// var client = new CopilotClient();
     ///
     /// // Connect to an existing server
-    /// var client = new CopilotClient(new CopilotClientOptions { CliUrl = "localhost:3000" });
+    /// var client = new CopilotClient(new CopilotClientOptions { CliUrl = "localhost:3000", UseStdio = false });
     ///
     /// // Custom CLI path with specific log level
     /// var client = new CopilotClient(new CopilotClientOptions