Validates every opt-in templates/<slug>/content-schema.json sidecar (spec: docs/template-schema-v2.md) against the JSON Schema in templates/schema/content-schema.schema.json, then bidirectionally against the sibling .dc.html: every declared slot id must resolve to a real {{ id }} hole, and (informationally, non-blocking) reports how many holes in the template have no schema entry yet. Coverage across all templates is reported but not required — like the visual-diff baselines, this is an intentionally incremental rollout (3 exemplars ship in v4.2.0). Verdict on window.__schemav2.