Clean up Voxtral Realtime HF weights after export

[mergennachin]

The downloaded model_weights/ directory (~20GB) was not removed
after export, causing it to be uploaded to S3 as part of the CI
artifact. Delete it after copying out the tokenizer since the
weights are fully baked into the .pte at that point.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/18289

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 1 Awaiting Approval, 2 New Failures, 51 Pending

As of commit 0186941 with merge base 5e265e6 ():

AWAITING APPROVAL - The following workflow needs approval before CI can run:

• Claude Code (gh)

NEW FAILURES - The following jobs have failed:

• pull / unittest / macos / macos-job (gh)
  backends/xnnpack/test/ops/test_conv2d.py::TestConv2d::test_fp16_conv2d
• Test CUDA Builds / export-model-cuda-artifact (mistralai, Voxtral-Mini-3B-2507, non-quantized) / linux-job (gh)
  RuntimeError: Command docker exec -t 1282e6f5abe7bc9b26260ac4305b3aafef8187615a732bb12a3bdd775567468e /exec failed with exit code 1

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[Copilot]

Pull request overview

Removes the large HuggingFace-downloaded Voxtral Realtime model_weights/ directory after export so it doesn’t get included in CI artifacts/S3 uploads, while still preserving the tokenizer needed at runtime.

Changes:

• Copy tekken.json tokenizer into the output artifact directory.
• Delete the downloaded model_weights/ directory after export for voxtral_realtime.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.

[manuelcandales]

@pytorchbot cherry-pick --onto release/1.2 -c release

[pytorchbot]

Cherry picking #18289

The cherry pick PR is at #18357 The following tracker issues are updated:

• [v1.2.0] Release Schedule and Tracker #17016 (comment)

Details for Dev Infra team

Raised by workflow job