Prepare GMR for motion-data-processing integration

[alik-git]

Prepares the T1 GMR branch to be used as a retargeting backend from the motion-data-processing pipeline.

Changes:

• Starts from the custom T1 support branch.
• Removes checked-in absolute symlinks to personal asset paths.
• Documents local SMPL-X body model placement under assets/body_models.
• Points custom T1 hand mesh references at Minerva robot assets instead of a GMR-owned assets/hands symlink.

Why:

• motion-data-processing should own the end-to-end dataset creation workflow before training.
• GMR should remain replaceable by another retargeting backend in that workflow.
• Robot assets should come from minerva_robot_assets, which is already present as a submodule in motion-data-processing.

Details:

• Verified the custom T1 XML loads with MuJoCo on the local mnv1 checkout.
• Remaining integration work is mostly about raw input normalization and runtime environment setup, not robot mesh ownership.