DECIDED 2026-09-23 (operator): own Providers list; stored rollup columns AND SharePoint View GroupBy/Aggregations; internal (not in /gallery). SPEC: CTs CatalogProduct/Offer/Review/Provider (Parent Item, StrictFields) in Parts.Procurement.xml reusing SourceUrl/URL/Body/ProductCategory/SKU/OppCurrencyCode/Vendor; spec fields with UN/ECE Rec 20 unit codes (WTT/VLT/AMP/KGM); rollups LowestOfferEur, LowestOfferProvider, EurPerWp, WeightPerWp, AvgIndependentRatingPct, IndependentReviewCount; Review Independence (Independent test / Third-party customer / Vendor-hosted); SiteTemplate.ProductCatalog (moderated, versioned) + SolarCatalog + Query.Catalog.Compare. Seed tools/catalog/build-solar-seed.py from the two sourced research files (pass 2: 13 EUR offers, 4 datasheet PDFs, GS1 GPC brick 10008389 'Solar Panels' confirmed; UNSPSC only class 26131900). Silence rules: partial numbers empty, raw text kept. After the list-page GUI merge.