add Nemotron-3-Diarization-preview (8 speaker and handle parallel speech)

I get early access to this model. The model is still private. I’ll add it as soon as they made public. It’s a brilliant model
https://huggingface.co/nvidia/Nemotron-3-Diarization-preview
cc
@MathieuDuponchelle I don’t know if you still need this, but I thought I’d let you know anyway hehe

Start with the linked Hugging Face page for Nemotron-3-Diarization-preview and confirm when the private model becomes public. Done means adding the model with support for eight speakers and parallel speech, but the issue names no repository files or tests and the work is already assigned.

Vom Indexierungsmodell aus dem Issue-Text verfasst.