Add NIST gear evaluation environment

[TuurStuyck]

Summary

Add NIST gear evaluation env

Detailed description

• Adds registered NIST gear assets and a DROID-only environment.
• Adds an evaluation-only NIST task with task observations, success/drop/timeout terminations, and success-rate metrics.
• Keeps training, policy, OSC, and new embodiment code out of this environment.