Add onnxscript to mcore extra dependencies

The removed Megatron-LM-workspace/setup.py directly listed onnxscript
as a dependency. With that workspace gone, onnxscript is only available
under megatron-core[dev] and megatron-core[lts] extras but the mcore
extra installs plain megatron-core. transformer_engine imports
onnxscript at module load time, causing --mcore-only tests to fail
with ModuleNotFoundError.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Kajal Jain <kajalj@nvidia.com>

Author: kajalj22

pyproject.toml

@@ -123,6 +123,7 @@ mcore = [
   "transformer-engine[pytorch,core_cu13] @ git+https://github.com/NVIDIA/TransformerEngine.git@v2.14.1",
   "megatron-core",
   "megatron-bridge",
+  "onnxscript",
   # Flash-attn version should be selected to satisfy both TE + vLLM requirements (xformers in particular)
   # https://github.com/NVIDIA/TransformerEngine/blob/v2.3/transformer_engine/pytorch/attention/dot_product_attention/utils.py#L108
   # https://github.com/facebookresearch/xformers/blob/8354497deb2c04c67fbb2e2ad911e86530da0e90/xformers/ops/fmha/flash.py#L76