Contract-verification approach: skill references/ files are curated
extracts (umlaut-transliterated, partial), so a content hash would
false-positive. Script verifies each extract declares an existing
plugin-shared master via its 'Master version:' footer and that any
named block resolves. Router full-mirror refs report MISSING-FOOTER
(informative, not drift). Test run: 22 checked, 0 drift, exit 0.
Philipp Sieder