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/JsonRpcNotification.cs

@@ -0,0 +1,27 @@
+using System.Text.Json.Nodes;
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents a notification message in the JSON-RPC protocol.
+/// </summary>
+/// <remarks>
+/// Notifications are messages that do not require a response and are not matched with a response message.
+/// They are useful for one-way communication, such as log notifications and progress updates.
+/// Unlike requests, notifications do not include an ID field, since there will be no response to match with it.
+/// </remarks>
+public class JsonRpcNotification : JsonRpcMessage
+{
+    /// <summary>
+    /// Gets or sets the name of the notification method.
+    /// </summary>
+    [JsonPropertyName("method")]
+    public required string Method { get; init; }
+
+    /// <summary>
+    /// Gets or sets optional parameters for the notification.
+    /// </summary>
+    [JsonPropertyName("params")]
+    public JsonNode? Params { get; init; }
+}