Bass absolute SDR floor, guitar/piano order pinned by stem energy,
finite + non-silent checks on the mono and 3 s slice paths, and the
test.failing comment cites ruling R7.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Radix-2 FFT and torch-compatible stft/istft (hann, center, reflect,
normalized). HTDemucs-6s ONNX separator mirroring demucs apply_model:
whole-mix normalisation, 343980-sample centred segments, 25% overlap
with triangular weights, _spec/_ispec around the graph, spectral +
time branch sum. Brief's guitar/bass > 3 dB criterion is unmet by the
model on t1b/1 and is kept as test.failing pending a ruling.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
