tune: ignore sub-millisecond write jitter in TX late detection

internal/app/engine.go

@@ -112,6 +112,7 @@ type RuntimeTransition struct {
 
 const (
 	lateBufferIndicatorWindow        = 5 * time.Second
+	writeLateTolerance               = 1 * time.Millisecond
 	queueCriticalStreakThreshold     = 3
 	queueMutedStreakThreshold        = queueCriticalStreakThreshold * 2
 	queueMutedRecoveryThreshold      = queueCriticalStreakThreshold
@@ -588,12 +589,13 @@ func (e *Engine) writerLoop(ctx context.Context) {
 		queueStats := e.frameQueue.Stats()
 		e.evaluateRuntimeState(queueStats, e.hasRecentLateBuffers())
 
-		if writeDur > e.chunkDuration {
+		lateOver := writeDur - e.chunkDuration
+		if lateOver > writeLateTolerance {
 			late := e.lateBuffers.Add(1)
 			e.lateBufferAlertAt.Store(uint64(time.Now().UnixNano()))
 			if late <= 5 || late%20 == 0 {
-				log.Printf("TX LATE: write=%s budget=%s over=%s queueResidence=%s pipeline=%s",
-					writeDur, e.chunkDuration, writeDur-e.chunkDuration, queueResidence, pipelineLatency)
+				log.Printf("TX LATE: write=%s budget=%s over=%s tolerance=%s queueResidence=%s pipeline=%s",
+					writeDur, e.chunkDuration, lateOver, writeLateTolerance, queueResidence, pipelineLatency)
 			}
 		}