Move Cortex-M backend tests from trunk.yml to pull.yml

[psiddh]

The test-mcu-cortex-m-backend CI job runs all Cortex-M pytests but was only in trunk.yml, meaning zero tests ran at diff time. Move it to pull.yml so regressions are caught on-diff before merge.

Authored with Claude.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/18308

• 📄 Preview Python docs built from this PR

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

❌ 1 Cancelled Job, 3 Unrelated Failures

As of commit 9dff79b with merge base 569cf41 ():

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / unittest-buck / macos / macos-job (gh)
  ##[error]The operation was canceled.

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• trunk / unittest-release / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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

[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.

[Copilot]

Pull request overview

Moves the Cortex-M backend CI job (test-mcu-cortex-m-backend) from the trunk workflow into the pull workflow so Cortex-M pytest regressions are caught during PR validation rather than only after merge.

Changes:

• Removed test-mcu-cortex-m-backend job from .github/workflows/trunk.yml.
• Added the same test-mcu-cortex-m-backend job to .github/workflows/pull.yml (builds the Cortex-M test runner and runs backends/cortex_m/test via pytest).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
.github/workflows/trunk.yml	Removes the Cortex-M backend test job from the trunk workflow job set.
.github/workflows/pull.yml	Adds the Cortex-M backend test job to PR CI so it runs pre-merge.

---

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