Add missing API docs

Author: kzu

src/Extensions.Grok/GrokClient.cs

@@ -4,12 +4,17 @@
 
 namespace Devlooped.Extensions.AI.Grok;
 
+/// <summary>Client for interacting with the Grok service.</summary>
+/// <param name="apiKey">The API key used for authentication.</param>
+/// <param name="options">The options used to configure the client.</param>
 public class GrokClient(string apiKey, GrokClientOptions options)
 {
     static ConcurrentDictionary<(Uri, string), GrpcChannel> channels = [];
 
+    /// <summary>Initializes a new instance of the <see cref="GrokClient"/> class with default options.</summary>
     public GrokClient(string apiKey) : this(apiKey, new GrokClientOptions()) { }
 
+    /// <summary>Gets the API key used for authentication.</summary>
     public string ApiKey { get; } = apiKey;
 
     /// <summary>Gets or sets the endpoint for the service.</summary>

src/Extensions.Grok/GrokClientExtensions.cs

@@ -1,9 +1,13 @@
-using Microsoft.Extensions.AI;
+using System.ComponentModel;
+using Microsoft.Extensions.AI;
 
 namespace Devlooped.Extensions.AI.Grok;
 
+/// <summary>Provides extension methods for <see cref="GrokClient"/>.</summary>
+[EditorBrowsable(EditorBrowsableState.Never)]
 public static class GrokClientExtensions
 {
+    /// <summary>Creates a new <see cref="IChatClient"/> from the specified <see cref="GrokClient"/> using the given model as the default.</summary>
     public static IChatClient AsIChatClient(this GrokClient client, string defaultModelId)
         => new GrokChatClient(client.Channel, client.Options, defaultModelId);
 }

src/Extensions.Grok/GrokClientOptions.cs

@@ -2,6 +2,7 @@
 
 namespace Devlooped.Extensions.AI.Grok;
 
+/// <summary>Options for configuring the <see cref="GrokClient"/>.</summary>
 public class GrokClientOptions
 {
     /// <summary> Gets or sets the service endpoint. </summary>