Space app: SLaT session cache, tone-mapper safety, CUDA/inference fixes

revert: remove sparse attention _linear inference-tensor clone hack

fix(sparse-attn): clone inference feats before Linear when grad is enabled

fix(sparse): spconv replace() must wire new feats into data.features

HF Space: drop ./vox2seq from requirements; vendored vox2seq_pytorch fallback

restore: full Space tree + assets (recover from minimal force-push); keep ZeroGPU app.py