Add inactivity safeguard and speaker diagnostics

MeetingAssistant.Tests/SpeakerAudioSampleCollectorTests.cs

@@ -1,5 +1,6 @@
 using MeetingAssistant.Recording;
 using MeetingAssistant.Transcription;
+using Microsoft.Extensions.Logging;
 using NAudio.Wave;
 
 namespace MeetingAssistant.Tests;
@@ -47,6 +48,27 @@ public sealed class SpeakerAudioSampleCollectorTests
         Assert.DoesNotContain(collector.Snapshot(), sample => sample.Speaker == "Guest01");
     }
 
+    [Fact]
+    public void CollectorLogsWhenSampleIsDiscardedBecauseSpeechIsTooShort()
+    {
+        var logger = new CapturingLogger();
+        var collector = new SpeakerAudioSampleCollector(
+            TimeSpan.FromMinutes(2),
+            maxSamplesPerSpeaker: 3,
+            minimumUninterruptedSpeechDuration: TimeSpan.FromSeconds(30),
+            maximumSegmentGap: TimeSpan.FromSeconds(1),
+            logger: logger);
+        collector.AppendAudio(CreateAudio(TimeSpan.FromSeconds(35)));
+
+        collector.TryAdd(Segment(0, 12, "Guest01", "one two three four five."));
+
+        var message = Assert.Single(
+            logger.Messages,
+            message => message.Contains("Discarding speaker identity sample for Guest01", StringComparison.Ordinal));
+        Assert.Contains("duration", message);
+        Assert.Contains("minimum duration", message);
+    }
+
     private static TranscriptionSegment Segment(
         double start,
         double end,
@@ -73,4 +95,30 @@ public sealed class SpeakerAudioSampleCollectorTests
         using var reader = new WaveFileReader(new MemoryStream(wavBytes));
         return reader.TotalTime;
     }
+
+    private sealed class CapturingLogger : ILogger
+    {
+        public List<string> Messages { get; } = [];
+
+        public IDisposable? BeginScope<TState>(TState state)
+            where TState : notnull
+        {
+            return null;
+        }
+
+        public bool IsEnabled(LogLevel logLevel)
+        {
+            return true;
+        }
+
+        public void Log<TState>(
+            LogLevel logLevel,
+            EventId eventId,
+            TState state,
+            Exception? exception,
+            Func<TState, Exception?, string> formatter)
+        {
+            Messages.Add(formatter(state, exception));
+        }
+    }
 }