Bi-DexHands assets + local_bottle_cap v2 (screw cap, quality meshes)
Supersedes PR #21 (same content, one revision newer on local_bottle_cap; opened as a new PR because the contributor token cannot push to an existing PR ref).
assets/bi-dexhands/{bottle_cap,cup,pen}: the Bi-DexHands/PartNet-Mobility source assets our five dexterous tasks port (slimmed: mobility.urdf + textured_objs + images + metadata; parts_render/point_sample dropped), with ATTRIBUTION.md (upstream commit dc41afd134cebfe4d80a5b861f0b8c15d734320a, Apache-2.0) and LICENSE.
assets/local_bottle_cap v2 — the project-authored water bottle the open_bottle_cap task ships, REDESIGNED from the v1 primitive-cylinder pull-off prop:
- real SCREW mechanism: cap_slide + cap_twist tied by a joint equality at 18 mm/turn; dry thread friction means the cap can only be TWISTED open (~2 ccw turns to the 3.5 cm gate) — a 20 N straight pull moves it <1 mm (measured);
- quality visuals: deterministic lathe-generated OBJ meshes (translucent bottle + water, frosted neck/spout, helical thread ridge generated at the SAME 18 mm/turn pitch as the equality, knurled cap); generator ships next to the XML;
- explicit cap<->bottle contact exclude (MuJoCo's parent-child filter is skipped when the parent welds to the world, i.e. in fixed-base standalone loads/tests);
- URDF twin chains the two joints for the one-time IsaacSim USD conversion (URDF cannot express the coupling; see the file header);
- checker gate unchanged (articulated_open min_open_m=0.035): the screw constrains how the travel is produced, not what is scored.
Physics regressions live in the code PR (somastacks/WUJI_SimBench#89): tests/test_bottle_cap_asset.py — no-creep / pull-resisted / twist-opens / tighten-blocked / pitch-vs-polycoef cross-check.