Improve progress reporting (#145)

* Improve progress reporting

- Enable injecting an `IProgress<>` into a tool call to report progress when the client has supplied a progress token
- Add a custom type for ProgressToken and ProgressNotification to map to the schema
- Simplify RequestId to match ProgressToken's shape
- Serialize StdioClientTransport's SendMessageAsync implementation
- Add strongly-typed names for all request methods
- Change all request IDs created by McpJsonRpcEndpoint to include a guid for that endpoint

* Address PR feedback

src/ModelContextProtocol/TokenProgress.cs

@@ -0,0 +1,31 @@
+using ModelContextProtocol.Protocol.Messages;
+using ModelContextProtocol.Server;
+using ModelContextProtocol.Shared;
+
+namespace ModelContextProtocol;
+
+/// <summary>
+/// Provides an <see cref="IProgress{ProgressNotificationValue}"/> tied to a specific progress token and that will issue
+/// progress notifications to the supplied endpoint.
+/// </summary>
+internal sealed class TokenProgress(IMcpServer server, ProgressToken progressToken) : IProgress<ProgressNotificationValue>
+{
+    /// <inheritdoc />
+    public void Report(ProgressNotificationValue value)
+    {
+        _ = server.SendMessageAsync(new JsonRpcNotification()
+        {
+            Method = NotificationMethods.ProgressNotification,
+            Params = new ProgressNotification()
+            {
+                ProgressToken = progressToken,
+                Progress = new()
+                {
+                    Progress = value.Progress,
+                    Total = value.Total,
+                    Message = value.Message,
+                },
+            },
+        }, CancellationToken.None);
+    }
+}