cms/backend/templates/bn is the authoring source for the bn page chrome;
core/templates/bn carries a mechanically-synced copy for guest-side plugin
templates. Byte-compares the sync set (head/toolbar/engagement templ +
asset_hooks.go) and fails with 'run make sync-templates in cms' on drift.
Skips when the repo has no backend/templates/bn or no sibling core checkout.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
