fix: isolate Windows sample playback for NAudio 3

MeetingAssistant.Tests/HealthEndpointTests.cs

@@ -1,6 +1,7 @@
 using System.Net;
 using System.Net.Http.Json;
 using MeetingAssistant.Recording;
+using MeetingAssistant.Workflow;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.AspNetCore.TestHost;
@@ -41,6 +42,17 @@ public sealed class HealthEndpointTests : IClassFixture<WebApplicationFactory<Pr
         Assert.Equal("ok", body?.Status);
     }
 
+    [Fact]
+    public async Task NeutralBuildReportsSpeakerPlaybackUnavailable()
+    {
+        var playback = factory.Services.GetRequiredService<IWorkflowRulesEditorSamplePlaybackQueue>();
+
+        var result = await playback.QueueAsync(1, [1, 2]);
+
+        Assert.Contains("Windows build", result);
+        Assert.DoesNotContain("Queued", result);
+    }
+
     [Fact]
     public async Task ApplicationStartupDeletesStaleTemporaryRecordings()
     {

MeetingAssistant/Program.cs

@@ -132,7 +132,11 @@ builder.Services.AddSingleton<IMeetingSummaryRetryRunner, MeetingSummaryRetryRun
 builder.Services.AddSingleton<IMeetingWorkflowRulesProvider, FileMeetingWorkflowRulesProvider>();
 builder.Services.AddSingleton<IMeetingWorkflowEngine, MeetingWorkflowEngine>();
 builder.Services.AddSingleton<IWorkflowRulesEditorInstructionBuilder, WorkflowRulesEditorInstructionBuilder>();
+#if WINDOWS
 builder.Services.AddSingleton<IWorkflowRulesEditorSamplePlaybackQueue, WorkflowRulesEditorSamplePlaybackQueue>();
+#else
+builder.Services.AddSingleton<IWorkflowRulesEditorSamplePlaybackQueue, UnavailableWorkflowRulesEditorSamplePlaybackQueue>();
+#endif
 builder.Services.AddSingleton<IWorkflowRulesEditorChatPipeline, WorkflowRulesEditorChatPipeline>();
 builder.Services.AddTransient<WorkflowRulesEditorChatViewModel>();
 #if WINDOWS

MeetingAssistant/Workflow/WorkflowRulesEditorSamplePlaybackQueue.cs

@@ -8,6 +8,7 @@ public interface IWorkflowRulesEditorSamplePlaybackQueue
     Task<string> QueueAsync(int sampleId, byte[] wavBytes, CancellationToken cancellationToken = default);
 }
 
+#if WINDOWS
 public sealed class WorkflowRulesEditorSamplePlaybackQueue : IWorkflowRulesEditorSamplePlaybackQueue, IDisposable
 {
     private readonly Channel<QueuedSample> channel = Channel.CreateUnbounded<QueuedSample>();
@@ -98,3 +99,13 @@ public sealed class WorkflowRulesEditorSamplePlaybackQueue : IWorkflowRulesEdito
 
     private sealed record QueuedSample(int SampleId, byte[] WavBytes);
 }
+#else
+public sealed class UnavailableWorkflowRulesEditorSamplePlaybackQueue : IWorkflowRulesEditorSamplePlaybackQueue
+{
+    public Task<string> QueueAsync(int sampleId, byte[] wavBytes, CancellationToken cancellationToken = default)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        return Task.FromResult("Speaker sample playback requires the Windows build of Meeting Assistant.");
+    }
+}
+#endif

docs/meeting-workflow-engine.md

@@ -1,5 +1,7 @@
 # Meeting Workflow Engine
 
+The interactive rules and identities editor can queue speaker samples for playback in the Windows build. The neutral build reports that playback requires the Windows build; it does not enqueue audio or initialize Windows audio devices.
+
 Meeting Assistant has a small local workflow engine for meeting-specific automation. It is intended for rules that are too personal or environment-specific to hard-code, such as adding default attendees, cleaning meeting titles, binding projects, or adding context notes when known speakers are detected.
 
 The workflow engine is deliberately narrow. It runs from a local YAML file, evaluates rules against the current meeting note read from disk, and applies a small set of meeting-safe mutations.

openspec/specs/meeting-session/spec.md

@@ -285,6 +285,8 @@ The rules and identities editor agent SHALL receive speaker identity tools to se
 
 The rules and identities editor agent SHALL receive speaker sample tools to list, read, delete, and queue playback of samples linked to identities. The delete sample tool SHALL refuse to delete the last remaining sample for an identity.
 
+Speaker sample playback SHALL use the Windows audio implementation only in the Windows-targeted build. The neutral build SHALL return an actionable unavailable response instead of reporting a sample as queued for playback.
+
 The first model request caused by each user-submitted chat turn SHALL send the `X-Initiator: user` header, while follow-up model requests within that same turn, such as tool-call continuations, SHALL send `X-Initiator: agent`.
 
 Meeting Assistant SHALL provide a diagnostic endpoint that opens the workflow rules editor through the same window service used by the tray menu.
@@ -337,6 +339,12 @@ Meeting Assistant SHALL provide a diagnostic endpoint that opens the workflow ru
 - **AND** it can list, read, delete, and queue playback of identity samples
 - **AND** deleting the last sample for an identity is refused
 
+#### Scenario: Neutral build refuses speaker playback
+- **GIVEN** Meeting Assistant runs from its neutral target build
+- **WHEN** an agent requests playback of a speaker sample
+- **THEN** the application reports that playback requires the Windows build
+- **AND** does not report that the sample was queued
+
 #### Scenario: User sends a rules-editing chat turn
 - **GIVEN** the rules editor chat window is open
 - **WHEN** the user types a prompt and presses Enter