Clarify expectations for when teams should release and update packages

We should clarify the recommended workflow when core packages are updated. When teams make changes to core packages, they are sometimes unsure about whether they should release them right away, and also whether they should be responsible for updating them in the extension and mobile projects.

We should document these expectations, perhaps in the contributor docs or PR template (or both).

Start by locating the contributor documentation and PR template mentioned in the issue, then review how core package changes relate to releases and updates in the extension and mobile projects. Confirm the expected responsibilities with maintainers before documenting them. Done means the release timing and update ownership are stated consistently in the selected documentation locations.

Written by the indexing model from the issue text.