Add debug logging to diagnose downloads folder issue

Jellyfin.Api/Helpers/StreamingHelpers.cs

@@ -386,6 +386,16 @@ public static class StreamingHelpers
 
         // Check if this is a full file download (no segments) vs HLS streaming
         var streamingRequest = state.BaseRequest as StreamingRequestDto;
+
+        // DEBUG: Write to file to see what's happening
+        try
+        {
+            var debugPath = "/tmp/jellyfin-downloads-debug.log";
+            var debugMsg = $"[{DateTime.Now:HH:mm:ss}] SegmentContainer={streamingRequest?.SegmentContainer ?? "NULL"}, Type={state.BaseRequest?.GetType().Name ?? "NULL"}\n";
+            System.IO.File.AppendAllText(debugPath, debugMsg);
+        }
+        catch { }
+
         if (streamingRequest?.SegmentContainer is null)
         {
             // Full file download - use disk-based transcode path