devops: add roll stable-test-runner automation

[mxschmitt]

NOTE: Tested in #36230.

[Copilot]

Pull Request Overview

A GitHub Actions workflow to automatically bump the @playwright/test runner version on a weekly schedule or via manual dispatch and open a PR with the update.

• Adds .github/workflows/roll_stable_test_runner.yml to run on Mondays at 10:00 UTC and on demand.
• Installs the beta runner, extracts its version, creates a branch, commits, and opens a pull request via GitHub App token.

Comments suppressed due to low confidence (2)

.github/workflows/roll_stable_test_runner.yml:5

• The comment says '3AM PST' but 10:00 UTC corresponds to 3 AM PDT (UTC-7) during daylight time; consider clarifying the local timezone or updating to 'PDT'.

#    # At 10:00am UTC  (3AM PST) every Monday

.github/workflows/roll_stable_test_runner.yml:39

• [nitpick] The commit message prefix 'test:' could be confused with test suite changes; consider using 'chore:' or 'build:' to indicate a dependency bump.

git commit -m "test: roll stable-test-runner to ${{ steps.bump.outputs.VERSION }}"

[github-actions]

Test results for "tests 1"

1 failed
❌ [webkit-library] › library/screenshot.spec.ts:44:14 › page screenshot › should work with a mobile viewport @webkit-ubuntu-22.04-node18

5 flaky

⚠️ [firefox-library] › library/inspector/cli-codegen-1.spec.ts:986:7 › cli codegen › should not throw csp directive violation errors @firefox-ubuntu-22.04-node18
⚠️ [firefox-page] › page/page-wait-for-function.spec.ts:104:3 › should work with strict CSP policy @firefox-ubuntu-22.04-node18
⚠️ [webkit-library] › library/browsercontext-pages.spec.ts:105:3 › should return bounding box with page scale @webkit-ubuntu-22.04-node18
⚠️ [webkit-page] › page/page-screenshot.spec.ts:345:5 › page screenshot › should work while navigating @webkit-ubuntu-22.04-node18
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:145:5 › should watch all @windows-latest-node18-1

39352 passed, 820 skipped
✔️✔️✔️

Merge workflow run.