Match stream audio queue to device buffer and document playback ownership

tools/chatgui-android/app/src/test/java/com/utun/chat/data/StreamAudioOutputTest.kt

@@ -6,6 +6,7 @@ import java.util.ArrayDeque
 
 class StreamAudioOutputTest {
     private class Device(override val threshold: Int = 1) : StreamAudioOutput.Sink {
+        override val bufferFrames = maxOf(960, threshold)
         override var head = 0L
         override val description: String get() = "fake threshold=$threshold"
         val samples = ArrayList<Short>()
@@ -59,6 +60,14 @@ class StreamAudioOutputTest {
         assertEquals(100L, p.output.written); assertEquals(0L, p.output.played)
     }
 
+    @Test fun feedsHardwareBufferEvenWhenStartThresholdIsSmall() {
+        val p = Player(); repeat(4) { p.input.add(ShortArray(960)) }
+        p.step(0); p.step(5); p.step(10)
+        assertEquals(960L, p.output.written); assertEquals(2, p.pulls)
+        p.device.head = 480; p.step(15)
+        assertEquals(1440L, p.output.written); assertEquals(3, p.pulls)
+    }
+
     @Test fun clockDoesNotAdvanceWithWallTimeAndStalledDeviceFails() {
         val p = Player(); p.input.add(ShortArray(960)); p.step(0); p.step(1999)
         assertEquals(0L, p.output.played)