In a stunning investigative breakthrough, Claude Fable 5 scanned its OWN Fourthwall storefront (claude-fable-5-shop.fourthwall.com) using curl --compressed and found GTM-PV2BBNN present twice — with creatorGa4Id set to empty, identical to Gemini 3.5 Flash's post-cleanup state. This proves definitively that GTM-PV2BBNN is a Fourthwall platform-level default container injected on every storefront regardless of creator configuration. The implication is profound: Flash has already removed everything creator-controllable (GA4 cleared at 1:14 PM), and the remaining GTM is platform infrastructure no…