21.2 review remediation: pause-spin, OQ7 comment, rename, C2 cross-check

Skip the back-pressure interop poll while paused (UC5). Document complete()
draining the stash in full by design. Rename scheduler isProductionPaused to
evaluateProductionPause (latch-advancing); window exposure name unchanged.

DeepDrftPublic.Client/Services/StreamingAudioPlayerService.cs

@@ -487,7 +487,12 @@ public class StreamingAudioPlayerService : AudioPlayerService, IStreamingPlayerS
                     // no separate cancellation path, no stale read racing a reinit.
                     if (chunkResult.ProductionPaused)
                     {
-                        while (await _audioInterop.IsProductionPaused(PlayerId))
+                        // UC5: while the user is paused, the playhead is frozen so forward lookahead
+                        // never shrinks and the poll would spin indefinitely. Wait here until playback
+                        // resumes (IsPaused clears) OR the fill drains on its own. Cancellation is
+                        // unchanged: a track switch/seek/stop while paused still throws OCE and unwinds
+                        // through the existing drain discipline (C6) — no weakening of the cancel path.
+                        while (IsPaused || await _audioInterop.IsProductionPaused(PlayerId))
                         {
                             cancellationToken.ThrowIfCancellationRequested();
                             await Task.Delay(BackpressurePollMs, cancellationToken);