Each harness re-runs the C++ side with --codec-fused after the
buffered run and gates on codes-full.bin equality between the two:
the decode path cannot change the predictor, so any divergence is a
bug. The fused run's perf lines land in the log as [Perf Fused] next
to the buffered ones, so every grid cell carries the buffered vs
fused comparison per backend and quant.
The fused audio itself is not scored here: greedy amplitudes vanish
in the streamed PCM_16 and the fused FP envelope has its own
validation against the stream path.
Pascal