New AST check scans handler render functions that build site settings
(getSiteSettings + doc["site_settings"]) and fails if they don't also set
siteSettings["toolbar"], so admin-toolbar injection can't silently regress
when a new public page type is added.
- toolbar.go: AST scanner; exempts renderListingPage (auto SEO pages) and
renderVersionPreview (carries its own preview banner).
- check_toolbar.go: registration at Seq 280 (ID "28").
- registry_test.go: +1 expected check; golden fixtures regenerated.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
