Move from MuJoCo 3.14.0 to 3.16 #152

Outcome

ssrobot and its MuJoCo stack run on MuJoCo 3.16 (the current release) instead of exactly 3.14.0.

Rationale

• MuJoCo 3.14.0 has a memory-corruption bug that 3.15 fixed. Compiling a builtin 2D texture with nchannel="1" corrupts the heap, and the process later crashes at an unrelated point (SIGSEGV/SIGTRAP). MuJoCo 3.15.0 and later reject the model with builtin textures must have 3 channels. Minimal reproduction:

  import gc, mujoco
  XML = '<mujoco><asset><texture name="t" type="2d" builtin="checker" width="8" height="8" nchannel="1"/></asset></mujoco>'
  for _ in range(300):
      m = mujoco.MjModel.from_xml_string(XML); del m; gc.collect()
  print("survived")  # never printed on 3.14.0; 3.15.0+ raise ValueError instead

• mj_viser is already verified on 3.16. It supports mujoco>=3.5. Its CI runs an installed-wheel end-to-end check on MuJoCo 3.5.0 (minimum), 3.14.0 (locked, to match ssrobot), and 3.16.0 (latest) across Python 3.11–3.14. That check compares geometry, poses, colors, and textures against MuJoCo's own mjv_updateScene and renderer.

• mj_viser's lock stays at 3.14.0 only because an environment containing ssrobot resolves to ssrobot's exact pin.

Scope

The exact pin originates in sscbirrt: sscbirrt._native_mujoco is built against libmujoco 3.14.0 and refuses any other version (sscbirrt/pyproject.toml, build and test requirements; docs/native-design.md). Upgrading therefore needs:

1. An sscbirrt release whose native MuJoCo adapter is built and tested against MuJoCo 3.16. This means updating build-system.requires, test-requires, the mujoco extra, and the auditwheel --exclude libmujoco.so.<version> line.
2. In ssrobot, moving the mujoco==3.14.0 pins (the mujoco extra and the base dependencies) and the sscbirrt range to that release, and updating MujocoRuntime's version check at open.
3. In mj_viser, bumping the lock to the same version afterward.

Non-goals

• Supporting several MuJoCo versions at once in sscbirrt's native adapter.
• Changing planning, runtime, or trace semantics.

Acceptance criteria

• sscbirrt's native MuJoCo module builds, loads, and passes its wheel test against MuJoCo 3.16.
• ssrobot pins that MuJoCo version and the matching sscbirrt release, and its test suite passes.
• MujocoRuntime accepts 3.16 and still refuses a mismatched MuJoCo at open.

Reproducible evidence

ssrobot CI green on the new pins. The reproduction above raises ValueError instead of crashing in the resulting environment.