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roboverse_data_wuji

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SomaStacks Inc 9

Add the Isaac Sim USD for local_juice_shot, so hand_track.open_juice_shot can render.

The task already pins roboverse_data/assets/local_juice_shot/usd/juice_shot.usd, but the asset
shipped MJCF + URDF + .obj meshes only, and metasim's IsaacSim handler spawns an
ArticulationObjCfg from a USD, never from the MJCF. Every IsaacSim run therefore died in
check_assets before Kit booted. MuJoCo is unaffected (it ignores usd_path).

Generated from the MJCF — not the URDF twin, which cannot express the screw coupling — with:

python scripts/mjcf_screwcap_to_usd.py \
    --mjcf roboverse_data/assets/local_juice_shot/juice_shot.xml \
    --out  roboverse_data/assets/local_juice_shot/usd/juice_shot.usd --spawnable

Self-contained, so the on-demand downloader (which walks MJCF references but NOT USD sublayers)
needs no extra_resources.

Contents: 4 meshes + 4 cylinders (juice column + label rings), ArticulationRootAPI on the root
rigid body, 3 rigid bodies (bottle / cap_screw / cap) and the two MJCF-named joints
cap_slide + cap_twist, chained bottle -> cap_screw -> cap. Two structural points that a USD
of this family has to get right, both of which fail silently:

• MuJoCo allows both cap DOFs on one body; a USD/PhysX articulation must be a TREE, so the
  massless cap_screw link is inserted (with a token mass, or PhysX derives zero from its absent
  colliders and refuses the articulation).
• The cap is a SIBLING of the bottle, not a child. Nesting it asserts a parent in USD namespace
  that contradicts the joint tree; PhysX resolves the two and drops one joint, leaving 1 DOF where
  the screw needs 2. IsaacLab reports 2 joints with the sibling layout.

The 3-start lead survives as wuji:screwPitchMPerRad = 0.00128916 m/rad (8.1 mm/turn) on the
prismatic joint. Materials follow the MJCF: transmissive PET wall (ior 1.52, opacity 0.22) over the
juice column (liquid ior 1.333), opaque white cap and orange label.

Verified on Isaac Sim 5.0.0 + IsaacLab 2.2.0: the scene boots and the articulation spawns with both
DOFs. NOT verified by a rendered rollout — this task has no published demos in either
trajs/parrot/ or trajs/parrot_60Hz/, which is the separate reason it is missing from the
44-task render array.

Sibling PR: #36 (local_bottle_cap). Code side: somastacks/WUJI_SimBench PR #114.