feat(superdex): published-wheel install, FR3 HF assets, unisim-core/unilab-rl 1.2.0

[TATP-233]

Summary

SuperDex 1.2.0 release integration (refs #1533, #1534):

• superdex optional extra: uv sync --extra superdex / pip install "unilab[superdex]" pulls the published SuperDex Physics/Robotics wheels via unisim-core[superdex] (CPython 3.12/3.13, Linux x86_64), replacing the temporary source-build setup. Bilingual installation docs simplified.
• MuJoCo guard fix: sim=mujoco runtime checks now guard on the mujoco_uni binding, since plain mujoco also arrives with the superdex extra.
• FR3 assets on Hugging Face: native bot assets (collision SDF, render GLB, license) hosted on unilabsim/unilab-robots like other robot meshes. The asset hub downloads bots/arms/fr3_v2 on first use; unilab-pull-assets --robot fr3_v2 pre-fetches; SUPERDEX_ASSETS_PATH / env.superdex_assets_root remain audited local overrides. Downloaded bots are excluded from the wheel and git. (HF-side upload: https://huggingface.co/datasets/unilabsim/unilab-robots/discussions/9 — needs an org maintainer to merge.)
• FR3 play defaults: native interactive viewer (single env); record playback stays unavailable without an MJCF visual model.
• Go2 task guide: bilingual train/eval (record, interactive, sim2sim) section in the SuperDex backend docs.
• Deps: unisim-core>=1.2.0, unilab-rl==1.2.0; uv.lock and uv.rocm.lock refreshed.
• README: ecosystem section lists downstream wuji_unilab and legged-manipulation_unilab (bilingual).

Validation

• make check — pass
• make test — 1611 passed, 21 skipped (includes native FR3 rollout and Go2 SuperDex owner tests)
• uv run pytest tests/scripts/test_check_docs.py -q — 19 passed
• cd docs/sphinx && UNILAB_DOCS_SKIP_AUTODOC=1 uv run --no-project --with-requirements requirements.txt sphinx-build -b html -n source build/html — success
• End-to-end: uv run train --algo ppo --task go2_joystick_flat --sim superdex (tiny config) and uv run eval --algo ppo --task go2_joystick_flat --sim superdex --load-run <run> (record video) both exit 0; uv run eval --algo ppo --task fr3_joint_target --sim superdex opens the native Polyscope viewer and exits 0; uv run unilab-pull-assets --robot fr3_v2 fetches 21 files.