RoboCasa: add GPU/regression CI coverage (+ control_freq wiring test)

[shuheng-liu]

Problem

RoboCasa currently has only CPU mock tests (tests/envs/test_robocasa.py): registration, factory dispatch, per-rank sharding, the version shim — none of which touch the real sim. LIBERO, by contrast, is exercised in gpu_test.yml and the nightly regression_test.yml, and has a config-wiring test (tests/envs/test_libero_control_freq.py).

So there's no sim-level regression protection for RoboCasa: a break in the wrapper / robosuite-master / robocasa-fork stack wouldn't be caught by CI.

Why it matters

The RoboCasa stack has several moving parts (robosuite pinned to a master commit, a packaging fork, a version shim, EGL rendering). Without GPU/regression coverage, regressions in any of those land silently.

Suggested approach

• A gpu-marked smoke test (construct / reset / step / render on a couple of tasks), gated on RoboCasa asset availability (skip cleanly when assets aren't present, since they're a ~5-10 GB runtime download).
• Decide how/whether to cache the assets for the GPU CI runners.
• A control_freq wiring unit test once RoboCasa: env.fps is inert — control_freq not wired to the sim #380 lands (config fps -> gym_kwargs["control_freq"] -> sim), mirroring test_libero_control_freq.py.

References

• tests/envs/test_robocasa.py, .github/workflows/gpu_test.yml, .github/workflows/regression_test.yml
• related: RoboCasa: env.fps is inert — control_freq not wired to the sim #380 (fps wiring)