refactor(libero-plus): rebase docker image on huggingface/lerobot-gpu

Mirror the libero/metaworld/robomme pattern: start from the nightly GPU
image (apt deps, python, uv, venv, lerobot[all] already there) and only
layer on what LIBERO-plus uniquely needs — its wand/ImageMagick build
deps, the non-extra runtime pips (robosuite==1.4.1, bddl, …), the
PYTHONPATH-shadowed fork, and the 6.4 GB assets.zip.

Drops ~50 lines of duplicated base setup (CUDA FROM, apt python, uv
install, user creation, venv init) the nightly already provides.
123 → 73 lines.

Also:
- Add libero_plus to docs/source/_toctree.yml under Benchmarks so
  doc-builder's TOC integrity check stops failing.
- Repoint the docs dataset link from pepijn223/libero_plus_lerobot to
  the canonical lerobot/libero_plus.
- Revert the stray uv.lock churn (revision/marker diff that crept in
  from an unrelated resolve — unrelated to LIBERO-plus).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/source/libero_plus.mdx

@@ -4,7 +4,7 @@ LIBERO-plus is a **robustness benchmark** for Vision-Language-Action (VLA) model
 
 - Paper: [LIBERO-plus: A Robustness Benchmark for VLA Models](https://github.com/sylvestf/LIBERO-plus)
 - GitHub: [sylvestf/LIBERO-plus](https://github.com/sylvestf/LIBERO-plus)
-- Dataset: [pepijn223/libero_plus_lerobot](https://huggingface.co/datasets/pepijn223/libero_plus_lerobot)
+- Dataset: [lerobot/libero_plus](https://huggingface.co/datasets/lerobot/libero_plus)
 
 ## Perturbation dimensions
 
@@ -138,7 +138,7 @@ If your policy was trained with different key names, pass a JSON remapping:
 
 A LeRobot-format training dataset for LIBERO-plus is available at:
 
-- [pepijn223/libero_plus_lerobot](https://huggingface.co/datasets/pepijn223/libero_plus_lerobot)
+- [lerobot/libero_plus](https://huggingface.co/datasets/lerobot/libero_plus)
 
 ### Example training command
 
@@ -147,7 +147,7 @@ lerobot-train \
     --policy.type=smolvla \
     --policy.repo_id=${HF_USER}/smolvla_libero_plus \
     --policy.load_vlm_weights=true \
-    --dataset.repo_id=pepijn223/libero_plus_lerobot \
+    --dataset.repo_id=lerobot/libero_plus \
     --env.type=libero_plus \
     --env.task=libero_spatial \
     --output_dir=./outputs/ \