* fix(#1864): balance <step> tags in settings-advanced.md §8 Model Policy
§8 Model Policy ended with </step> but had no matching opening tag (5 opens /
6 closes), leaving it as loose inter-step content. Add the missing
<step name="model_policy"> opener so the section is a proper step.
- gsd-core/workflows/settings-advanced.md: add <step name="model_policy">
- tests/workflow-step-tag-balance.test.cjs: regression guard — every top-level
workflow must have balanced <step>/</step> (fenced code stripped), plus a
focused assertion that §8 is wrapped in model_policy.
- goldens + workflow-size baseline recaptured.
Closes#1864
* docs(#1864): backfill changeset pr 2014
