Add live end-to-end integration test for the VoiceAgent loop

Lands with the VoiceAgent core it covers. Speaks a question with Amazon Polly,
appends a second of trailing silence so Amazon Transcribe endpoints the
utterance, feeds it through VoiceAgent.Create (Transcribe -> Bedrock -> Polly),
and asserts the loop transcribed the caller, took a turn, produced reply text,
and produced spoken audio. Always runs against live AWS.

The Bedrock model is overridable via SPEECH_MEAI_TEST_MODEL_ID (default
us.anthropic.claude-haiku-4-5-20251001-v1:0) so the test tracks an invokable
model as the catalog changes.

Verified: passes against live AWS in us-west-2.

Author: GarrettBeatty

test/AWS.Speech.MEAI.IntegrationTests/VoiceAgentLoopIntegrationTests.cs

@@ -0,0 +1,84 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+#if NET8_0_OR_GREATER
+using Amazon.Polly;
+using Microsoft.Extensions.AI;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Xunit;
+
+namespace AWS.Speech.MEAI.IntegrationTests;
+
+/// <summary>
+/// Live end-to-end integration test for the <see cref="VoiceAgent"/> pipeline: Amazon Transcribe for
+/// speech-to-text, Amazon Bedrock for reasoning, and Amazon Polly for text-to-speech. Always runs
+/// against live AWS with the ambient credential and region chain.
+/// </summary>
+[Trait("Category", "Integration")]
+public class VoiceAgentLoopIntegrationTests
+{
+    // Overridable so the test tracks a current, invokable model as Bedrock's catalog changes.
+    private static string ModelId =>
+        Environment.GetEnvironmentVariable("SPEECH_MEAI_TEST_MODEL_ID")
+        ?? "us.anthropic.claude-haiku-4-5-20251001-v1:0";
+
+    [Fact]
+    [Trait("IntegrationTest", "Speech")]
+    public async Task RunAsync_TranscribesReasonsAndSpeaks()
+    {
+        // Speak a question with Amazon Polly, then feed it through the full loop. A second of trailing
+        // silence lets Transcribe endpoint the utterance so the agent takes its turn.
+        using var polly = new AmazonPollyClient();
+        var tts = polly.AsITextToSpeechClient(defaultSampleRateHertz: 16000);
+        var question = await tts.GetAudioAsync(
+            "In one word, what color is a clear daytime sky?", cancellationToken: TestContext.Current.CancellationToken);
+        var speech = question.Contents.OfType<DataContent>().Single().Data.ToArray();
+
+        var pcm = new byte[speech.Length + 32000]; // ~1s trailing silence at 16 kHz mono 16-bit
+        Array.Copy(speech, pcm, speech.Length);
+
+        await using var agent = VoiceAgent.Create(options =>
+        {
+            options.ModelId = ModelId;
+            options.Instructions = "You are concise. Answer in one short sentence.";
+        });
+
+        using var timeout = CancellationTokenSource.CreateLinkedTokenSource(TestContext.Current.CancellationToken);
+        timeout.CancelAfter(TimeSpan.FromSeconds(120));
+
+        var kinds = new HashSet<VoiceAgentUpdateKind>();
+        var assistantText = new System.Text.StringBuilder();
+        long assistantAudioBytes = 0;
+        string? userFinal = null;
+
+        using var microphone = new MemoryStream(pcm);
+        await foreach (var update in agent.RunAsync(microphone, timeout.Token))
+        {
+            kinds.Add(update.Kind);
+            switch (update.Kind)
+            {
+                case VoiceAgentUpdateKind.UserTranscriptFinal:
+                    userFinal = update.Text;
+                    break;
+                case VoiceAgentUpdateKind.AssistantText when update.Text is { Length: > 0 }:
+                    assistantText.Append(update.Text);
+                    break;
+                case VoiceAgentUpdateKind.AssistantAudio when update.Audio is { } audio:
+                    assistantAudioBytes += audio.Length;
+                    break;
+            }
+        }
+
+        Assert.False(string.IsNullOrWhiteSpace(userFinal), "The caller's utterance was not transcribed.");
+        Assert.Contains(VoiceAgentUpdateKind.TurnStarted, kinds);
+        Assert.Contains(VoiceAgentUpdateKind.TurnComplete, kinds);
+        Assert.False(string.IsNullOrWhiteSpace(assistantText.ToString()), "The agent produced no reply text.");
+        Assert.True(assistantAudioBytes > 0, "The agent produced no spoken audio.");
+    }
+}
+#endif