* Studio: training survives a non-writable HF datasets cache
A shared HF datasets cache can contain subtrees owned by another user
(for example populated by an earlier root-run job). datasets then dies
with "[Errno 13] Permission denied: ..._builder.lock" while locking
the cached builder and the training run fails. load_dataset in the
training worker and trainer now goes through a wrapper that catches the
EACCES and rebuilds the dataset in a Studio-owned cache under
cache_root()/hf-datasets, logging the fallback.
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Scope the HF_DATASETS_CACHE override to the fallback load
* Route non-streaming dataset preview loads through the cache-safe wrapper
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
