task-release: Add a job summary to the release workflows

[jtrobles-cdd]

Context

A release runs on a schedule in most of the callers, and until now its outcome was only visible by opening the log of the run. Both release task workflows now write a GitHub Actions job summary whose first line under the heading is the URL of the pull request they opened, followed by a short list of what is being released and who was asked to review it.

Decisions Somebody Should Weigh In On

• The URL is written bare rather than as a Markdown link, so that it can be copied out of the rendered summary as easily as it is read. GitHub autolinks it.
• A run that finds nothing to release writes a summary of its own rather than leaving it empty, because that is the outcome of most scheduled runs and an empty summary does not distinguish it from a run that failed before it got started.
• The reviewer bullets are appended by a later step than the one that writes the heading and the URL, so they only render as a continuation of the same list if GitHub concatenates what each step wrote without inserting anything between them.
• Release and Publish names the release pull request it came from in the summary, which Release and Deploy to Production has no equivalent of, so the two summaries are not identical in shape.

What I Could Not Verify

• Neither workflow can be exercised outside a real release, so the summary has never been rendered by GitHub. What the first real run has to show is whether the bullets written by two separate steps do join into one list, and whether the bare URL autolinks in a job summary as it does in a comment. Both degrade into something still readable if they do not.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud