b32fce1d74
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>