CI: version PRs opened by automation never get TypeScript or Python CI #5110

Problem

The Version Packages PR (changesets action) and the Prepare Python Release PR are opened and updated with the workflow's GITHUB_TOKEN, which starts no workflows. RELEASING.md and the release skill say to close and reopen such a PR to start CI, but since #5048 the TypeScript and Python workflows run on push only: a reopen fires pull_request, which reaches only dco.yml. So an automated version PR never gets TypeScript or Python CI; #4941 had no check runs.

Found by Copilot on the v1.0.0 merge PR #5090. v1.0.0 was not affected (its version changes were made by hand), but the next release would be.

Expected

A version PR opened by automation is validated by the same TypeScript and Python CI as any other PR before it merges: for example, the workflows dispatch (or workflow_call) CI for the PR's head after opening or updating it, or the PR is opened with a credential whose events start workflows (the GitHub App of #5061). RELEASING.md and the release skill describe the working path, not close-and-reopen.