Two CodeRabbit findings from #7063 (#13 and #14) are deferred because
worksplit-multigpu's initial release scope is NVIDIA-only QA. Leave a
TODO at the unconditional torch.cuda.set_device call and at the
post-aggregation point so the required guards/synchronize are easy to
find when multigpu support is extended to XPU/NPU/MPS/CPU/DirectML.
Amp-Thread-ID: https://ampcode.com/threads/T-019e4a00-fe3d-76bd-a2f2-a8c8c4040082
Co-authored-by: Amp <amp@ampcode.com>