Clean up namespaces (#410)

No meaningful code changes, just lots of namespace shuffling to have fewer namespaces and to put things in better namespaces.

src/ModelContextProtocol/Protocol/GetPromptResult.cs

@@ -0,0 +1,42 @@
+using Microsoft.Extensions.AI;
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents a server's response to a <see cref="RequestMethods.PromptsGet"/> request from the client.
+/// </summary>
+/// <remarks>
+/// <para>
+/// For integration with AI client libraries, <see cref="GetPromptResult"/> can be converted to
+/// a collection of <see cref="ChatMessage"/> objects using the <see cref="AIContentExtensions.ToChatMessages"/> extension method.
+/// </para>
+/// <para>
+/// See the <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/">schema</see> for details.
+/// </para>
+/// </remarks>
+public class GetPromptResult
+{
+    /// <summary>
+    /// Gets or sets an optional description for the prompt.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This description provides contextual information about the prompt's purpose and use cases.
+    /// It helps developers understand what the prompt is designed for and how it should be used.
+    /// </para>
+    /// <para>
+    /// When returned from a server in response to a <see cref="RequestMethods.PromptsGet"/> request,
+    /// this description can be used by client applications to provide context about the prompt or to
+    /// display in user interfaces.
+    /// </para>
+    /// </remarks>
+    [JsonPropertyName("description")]
+    public string? Description { get; set; }
+
+    /// <summary>
+    /// Gets or sets the prompt that the server offers.
+    /// </summary>
+    [JsonPropertyName("messages")]
+    public List<PromptMessage> Messages { get; set; } = [];
+}