Cross-repository changelog automation added to release pipeline

The release pipeline automatically triggers changelog drafts on the marketing site when a new version is published. This automates the initialization of release notes across repositories.

A new dispatch job waits for the primary release processes to finish so that assets like the precise Docker image URL are finalized. Once the release is confirmed, it fires a cross-repository webhook to the marketing site.

The payload uses a standard repository dispatch action to pass along the published package version, providing the receiving repository with the exact version string needed to template out a draft pull request.