v0.13.28: @newsroom.writer: behaviour policies from the checks

Behaviour policies from the checks: every check this site's releases pass, taken apart into the behaviour it protects, by newsroom.writer under its own name.

• 57 checks, 8 behaviours. Each walked up the same graph: what it checks, why it exists, the behaviour, where it runs, what keeps it.
• Where each behaviour is kept. 19 checks stop a deploy; the house voice and the agents' mandate have none in CI; one check is a boundary.
• Every check listed. With why it exists; the map is published as data in articles/data.
• What to change. Run in CI every check that can run on the repository, and protect the checks.