Automatically set the logging through stderr for MCP servers

This prevents default logging to console to disrupt the stdio protocol.

We do this only and automatically when AddMcpServer was invoked previously.

Author: kzu

src/Smith/App.cs

@@ -1,5 +1,8 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using ModelContextProtocol.Server;
 
 namespace Smith;
 
@@ -8,6 +11,30 @@ namespace Smith;
 /// </summary>
 public static class App
 {
+    class AppBuilder(IServiceCollection services)
+    {
+        public IServiceCollection Services => services;
+    }
+
+    class AppServiceFactory(HostApplicationBuilder host) : IServiceProviderFactory<AppBuilder>
+    {
+        public AppBuilder CreateBuilder(IServiceCollection services) => new(services);
+
+        public IServiceProvider CreateServiceProvider(AppBuilder builder)
+        {
+            // If MCP server was registered with AddMcpServer, then tune logging to prevent 
+            // stdio noise from breaking the protocol.
+            if (host.Services.AsEnumerable().Any(x => x.ServiceType == typeof(IConfigureOptions<McpServerOptions>)))
+            {
+                host.Logging.AddConsole(consoleLogOptions =>
+                {
+                    consoleLogOptions.LogToStandardErrorThreshold = LogLevel.Trace;
+                });
+            }
+            return builder.Services.BuildServiceProvider();
+        }
+    }
+
     /// <summary>
     /// Invokes the <see cref="Host.CreateApplicationBuilder(string[]?)"/> with additional pre-configured defaults.
     /// </summary>
@@ -19,7 +46,12 @@ public static class App
     /// </remarks>
     /// <param name="args">The command line args.</param>
     /// <returns>The initialized <see cref="HostApplicationBuilder"/>.</returns>
-    public static HostApplicationBuilder CreateBuilder(string[]? args) => Host.CreateApplicationBuilder(args);
+    public static HostApplicationBuilder CreateBuilder(string[]? args)
+    {
+        var host = Host.CreateApplicationBuilder(args);
+        host.ConfigureContainer(new AppServiceFactory(host));
+        return host;
+    }
 
     /// <summary>
     /// Builds the host app and registers the provided <paramref name="main"/> function as a hosted service to be