chore: import upstream snapshot with attribution

dotnet/samples/03-workflows/_StartHere/01_Streaming/01_Streaming.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.Workflows\Microsoft.Agents.AI.Workflows.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/03-workflows/_StartHere/01_Streaming/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+using Microsoft.Agents.AI.Workflows;
+
+namespace WorkflowStreamingSample;
+
+/// <summary>
+/// This sample introduces streaming output in workflows.
+///
+/// While 01_Executors_And_Edges waits for the entire workflow to complete before showing results,
+/// this example streams events back to you in real-time as each executor finishes processing.
+/// This is useful for monitoring long-running workflows or providing live feedback to users.
+///
+/// The workflow logic is identical: uppercase text, then reverse it. The difference is in
+/// how we observe the execution - we see intermediate results as they happen.
+/// </summary>
+public static class Program
+{
+    private static async Task Main()
+    {
+        // Create the executors
+        UppercaseExecutor uppercase = new();
+        ReverseTextExecutor reverse = new();
+
+        // Build the workflow by connecting executors sequentially
+        WorkflowBuilder builder = new(uppercase);
+        builder.AddEdge(uppercase, reverse).WithOutputFrom(reverse);
+        var workflow = builder.Build();
+
+        // Execute the workflow in streaming mode
+        await using StreamingRun run = await InProcessExecution.RunStreamingAsync(workflow, input: "Hello, World!");
+        await foreach (WorkflowEvent evt in run.WatchStreamAsync())
+        {
+            if (evt is ExecutorCompletedEvent executorCompleted)
+            {
+                Console.WriteLine($"{executorCompleted.ExecutorId}: {executorCompleted.Data}");
+            }
+            else if (evt is WorkflowErrorEvent workflowError)
+            {
+                Console.ForegroundColor = ConsoleColor.Red;
+                Console.Error.WriteLine(workflowError.Exception?.ToString() ?? "Unknown workflow error occurred.");
+                Console.ResetColor();
+            }
+            else if (evt is ExecutorFailedEvent executorFailed)
+            {
+                Console.ForegroundColor = ConsoleColor.Red;
+                Console.Error.WriteLine($"Executor '{executorFailed.ExecutorId}' failed with {(executorFailed.Data == null ? "unknown error" : $"exception {executorFailed.Data}")}.");
+                Console.ResetColor();
+            }
+        }
+    }
+}
+
+/// <summary>
+/// First executor: converts input text to uppercase.
+/// </summary>
+internal sealed class UppercaseExecutor() : Executor<string, string>("UppercaseExecutor")
+{
+    /// <summary>
+    /// Processes the input message by converting it to uppercase.
+    /// </summary>
+    /// <param name="message">The input text to convert</param>
+    /// <param name="context">Workflow context for accessing workflow services and adding events</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>The input text converted to uppercase</returns>
+    public override ValueTask<string> HandleAsync(string message, IWorkflowContext context, CancellationToken cancellationToken = default) =>
+        ValueTask.FromResult(message.ToUpperInvariant()); // The return value will be sent as a message along an edge to subsequent executors
+}
+
+/// <summary>
+/// Second executor: reverses the input text and completes the workflow.
+/// </summary>
+internal sealed class ReverseTextExecutor() : Executor<string, string>("ReverseTextExecutor")
+{
+    /// <summary>
+    /// Processes the input message by reversing the text.
+    /// </summary>
+    /// <param name="message">The input text to reverse</param>
+    /// <param name="context">Workflow context for accessing workflow services and adding events</param>
+    /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests.
+    /// The default is <see cref="CancellationToken.None"/>.</param>
+    /// <returns>The input text reversed</returns>
+    public override ValueTask<string> HandleAsync(string message, IWorkflowContext context, CancellationToken cancellationToken = default)
+    {
+        // Because we do not suppress it, the returned result will be yielded as an output from this executor.
+        return ValueTask.FromResult(string.Concat(message.Reverse()));
+    }
+}