TASK 4 ship step 4: WASAPI audio capture — NAudio loopback + mic behind an IAudioSource seam, AudioMixer driving AudioLevel while live, pure level meter + WaveToFloat, NAudio.Wasapi 2.2.1 (MIT, notices item 9) — 139 tests passing, 0 warnings

Services/Audio/IAudioSource.cs

@@ -0,0 +1,22 @@
+namespace ytLive.Services.Audio;
+
+/// <summary>
+/// A live audio capture source (TASK 4 ship step 4 seam): produces PCM float
+/// chunks, runs only while live. The default implementations wrap NAudio's
+/// WASAPI capture (mic) / loopback (desktop/game); the mixer and the tests
+/// consume this interface, never NAudio directly.
+/// </summary>
+public interface IAudioSource : IDisposable
+{
+    /// <summary>Starts capturing. Safe to call only once per Stop.</summary>
+    void Start();
+
+    /// <summary>Stops capturing; a later Start begins a fresh session.</summary>
+    void Stop();
+
+    /// <summary>Raises each captured chunk (interleaved PCM float, -1..1).</summary>
+    event Action<AudioSample>? SampleReady;
+
+    /// <summary>Raises when capture dies or fails to start (e.g. no device).</summary>
+    event Action<Exception>? Failed;
+}