Implement MCP task support (SEP-1686) (#1170)

Co-authored-by: Stephen Halter <halter73@gmail.com>

samples/LongRunningTasks/Tools/TaskTools.cs

@@ -0,0 +1,31 @@
+using ModelContextProtocol;
+using ModelContextProtocol.Protocol;
+using ModelContextProtocol.Server;
+using System.ComponentModel;
+
+namespace LongRunningTasks.Tools;
+
+/// <summary>
+/// Demonstrates creating and returning tasks via <see cref="IMcpTaskStore"/>.
+/// </summary>
+[McpServerToolType]
+public class TaskTools(IMcpTaskStore taskStore)
+{
+    /// <summary>
+    /// Submits a job to the task store and returns a task handle for polling.
+    /// </summary>
+    [McpServerTool]
+    [Description("Submits a job and returns a task that can be polled for completion.")]
+    public Task<McpTask> SubmitJob(
+        [Description("A label for the job")] string jobName,
+        RequestContext<CallToolRequestParams> context,
+        CancellationToken cancellationToken)
+    {
+        return taskStore.CreateTaskAsync(
+            new McpTaskMetadata { TimeToLive = TimeSpan.FromMinutes(10) },
+            context.JsonRpcRequest.Id!,
+            context.JsonRpcRequest,
+            context.Server.SessionId,
+            cancellationToken);
+    }
+}