* fix(rocm): stop overwriting ROCR_VISIBLE_DEVICES in apply_gpu_ids
ROCR_VISIBLE_DEVICES uses HSA agent-level indexing, not physical GPU
indices. Setting it to a bare integer breaks multi-GPU ROCm systems
where the parent already set ROCR_VISIBLE_DEVICES=0,1: narrowing to
1 causes torch.cuda.is_available() to return False in the training
worker, producing a misleading 'no HIP accelerator' error even on a
correctly configured ROCm host.
HIP_VISIBLE_DEVICES is sufficient for GPU selection on ROCm.
Leave ROCR_VISIBLE_DEVICES inherited from the parent environment.
* test(rocm): update apply_gpu_ids test to assert ROCR_VISIBLE_DEVICES is not overwritten
3964f44f02