Pin RoboTwin to the Hopper-safe CuRobo revision

[gpulost]

Summary

• add a benchmark-maintained overlay patch for the pinned RoboTwin submodule;
• pin the base RoboTwin installer and the TinyVLA/DexVLA environment files to
  gpulost/curobo@3490ef46d4ffbbf6756b91fb13b68215828533b0;
• apply the overlay during the Docker build; and
• document the same patch step for local installation.

Motivation

RoboTwin currently clones the floating NVlabs/curobo default branch in its
base installer, while two policy environment files pin an older CuRobo commit.
Those paths can install the original fused LBFGS reduction, whose synchronized
warp masks have undefined behavior on partial warps and can fail on Hopper.

The pinned commit contains the Hopper-safe LBFGS reduction proposed in
NVlabs/curobo#708. The overlay keeps the RoboTwin gitlink unchanged while
making all three known CuRobo installation paths deterministic.

Validation

• git apply --check succeeds against RoboTwin
  daef39a2f43226fb5af87552544e03d1f1bc70d9.
• GNU patch --dry-run -d RoboTwin -p1 succeeds, matching the Docker build
  path.
• The applied RoboTwin installer passes bash -n.
• The applied installer and both policy requirement files resolve to the same
  immutable CuRobo commit.
• git diff --check passes.
• The pinned CuRobo kernel and CUDA test are byte-identical to the version
  validated on H20 for shared and non-shared paths at dimensions 7, 31, 33,
  175, and 224.

The full multi-environment Docker image was not rebuilt as part of this change.