Cross-link to demucs-onnx Python package (open-source ONNX export tooling on PyPI)

Cross-link to demucs-onnx Python package (open-source ONNX export tooling on PyPI)

feat: add htdemucs_ft_vocals_fp16weights.onnx (fp16-weights compact-storage variant)

docs: add fp16-weights compact-storage variant section

Add htdemucs_ft_vocals.onnx

Initial release: parity-verified ONNX export of htdemucs_ft vocals specialist

initial commit