[google-admin]

Requested by @crwilcox (crwilcox@google.com) ahead of GitHub's November 2, 2026 default policy enforcement blocking pull_request_target workflows on public repositories without an explicit Actions event policy:

• https://github.blog/changelog/2026-09-17-workflow-execution-protections-in-github-actions-generally-available/
• https://docs.github.com/en/actions/reference/security/securely-using-pull_request_target

Summary

Switches validate-pr-title/validate-pr-title.yaml from on: pull_request_target to on: pull_request:

• All configured types (opened, reopened, edited, synchronize, assigned, labeled, ready_for_review, review_requested) are supported identically on pull_request.
• amannn/action-semantic-pull-request only reads pull request title metadata using the default GITHUB_TOKEN (no repository secrets, labels, or comments needed).
• Once merged to main, .github/workflows/sync-common-workflows.yaml will propagate this update across the downstream shaka-project repositories using validate-pr-title.yaml.

[google-cla]

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[crwilcox]

I'll recommit this as myself and close this PR

[crwilcox]

#71