a851d3587c
Addresses adversarial-review findings: a canonical file carrying a stray Shopify-signature name (e.g. SEO Title) no longer misdetects as Shopify and silently drops canonical Type / corrupts the weight unit (kg->g). A canonical-distinctive column (Description/Variant Cost/Variant Weight/Google Product Category/Variant Volume/Tax ID/Position) now vetoes detection, so detection leans conservative (under-detection warns; over-detection corrupts). Also closes the dual-named-column shadow (Body (HTML)+Description) and the stale-weight-unit-on-clear case. Tests cover all three. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>