A self-contained guide (docs/reference/playbook-authoring.md) to the contract
between a playbook and Steward's run UI — the `# description:` comment,
vars/vars_prompt → fill-in fields, secret naming, hosts: all targeting,
managed credentials, and idempotency. Includes a "what Steward reads" summary
table, the metadata/extensibility note (only `# description:` today; reserved
`# steward:<key>:` namespace for future keys), and an annotated example.
Meant to be fed to another session authoring Steward-friendly playbooks.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
