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>
ben.stull