fix(ci): exclude promotion PR from pr-autoupdate

[castrojo]

Problem

pr-autoupdate.yml was running gh pr update-branch on auto/promote-testing-to-main whenever main advanced. This created a merge commit on the squash branch which:

1. Changed the tree, defeating the tree-identity check in reusable-promote-squash.yml
2. Triggered a force-push on the next promote run
3. Dismissed the maintainer approval (dismiss_stale_reviews: true)

Result: approvals could never survive to merge. The PR regenerated itself in a loop.

Fix

• Exclude auto/promote-testing-to-main from pr-autoupdate.yml — the promote workflow is the sole owner of that branch and always rebuilds from fresh origin/main
• Flipped dismiss_stale_reviews to false in branch protection via API — a valid approval now survives the nightly squash rebuild when tree content is identical

Testing

Branch protection change is live. The next promote run + approval will verify the fix.

Summary by CodeRabbit

• Chores
  • Updated pull request automation workflow configuration to exclude certain branches from auto-update processing.

[github-actions]

Thanks for the PR! A maintainer will review it.

While you wait, make sure these pass locally:

just validate        # element graph check
just build default   # build the image
just boot-test       # confirm the desktop boots (exits 0 = pass)
just lint            # bootc container lint

If this PR fixes a bug, add verify steps to the linked issue so users can confirm the fix on their hardware after the next nightly ships:

```verify
ujust <something>   # what users should run to confirm the fix
```

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 10e16eb1-82dd-4332-91e8-45cec47ae308

📥 Commits

Reviewing files that changed from the base of the PR and between 7b3a36c and 54eeaa7.

📒 Files selected for processing (1)

• .github/workflows/pr-autoupdate.yml

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📝 Walkthrough

Walkthrough

The pr-autoupdate.yml workflow is updated to exclude PRs whose head branch is auto/promote-testing-to-main from automatic updates. The JQ filter in the gh pr list command gains an additional exclusion condition, and new comments explain that this branch's merge/force-push behavior can alter tree identity and dismiss approvals.

Changes

PR Auto-Update Exclusion for Promote Branch

Layer / File(s)	Summary
Exclude promote branch from pr-autoupdate filter .github/workflows/pr-autoupdate.yml	Extends the JQ filter to skip PRs where headRefName equals auto/promote-testing-to-main, and adds comments explaining that the promote workflow's merge/force-push can change tree identity and dismiss approvals.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related issues

• ci(promote): auto-close stale promote PR before opening a new one #895: This PR directly implements the exclusion of auto/promote-testing-to-main from pr-autoupdate.yml, which addresses management coordination between the two workflows discussed in that issue.

Possibly related PRs

• projectbluefin/dakota#822: Adjusts the promote-to-main pipeline that produces the auto/promote-testing-to-main branch that this PR now excludes from auto-updates.
• projectbluefin/dakota#931: Adds a complementary safeguard in sync-main-to-testing.yml to protect the auto/promote-testing-to-main branch, part of the same family of workflow coordination changes.

Suggested labels

area/ci, pr/needs-review, type/bug, priority/p1

Suggested reviewers

• p5
• tulilirockz

Poem

🐇 Hippity-hop, the promote branch must roam,
Free from merge bumps that muddle its home.
A filter now guards what the JQ weaves,
No auto-updates to ruffle its leaves!
The promote workflow tends its own tree — 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title accurately summarizes the main change: excluding the promotion PR branch from the auto-update workflow to prevent cascading CI failures.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/promotion-pr-stability

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