Add governed buildings register snapshot

docs/DATA_SOURCES.md

@@ -329,12 +329,44 @@ quality metrics.
 
 ## Gebouwenregister
 
-- Naam: Gebouwenregister Vlaanderen
-- Type: vector/API/metadata
-- Gebruik: gebouwmetadata en statusinformatie
-- Toegang: nader te bepalen
-- Cache: PostGIS/metadata tabellen
-- Prioriteit: V2
+The governed operator `scripts/provision_buildings_addresses_register.py`
+reads the official Digitaal Vlaanderen OGC API Features collections
+`Gebouw`, `Gebouweenheid` and `Adres`. The source is continuously updated;
+GeoIntel therefore creates a dated snapshot rather than claiming an annual
+historical series. Raw response pages, request URLs and SHA256 checksums are
+retained as operator evidence.
+
+Building polygons are clipped against the exact persisted Area in
+EPSG:31370, transformed to EPSG:4326 and persisted through the normal Dataset
+upload route with `source_name=digitaal_vlaanderen_buildings_addresses_register`
+and `reference_layer_name=building_registry`. Register lifecycle state remains
+separate from GRB geometry. Each register building receives an explicit
+`matched`, `review`, `ambiguous` or `unmatched` GRB reconciliation result; a
+low-confidence or duplicate match is never silently promoted.
+
+Building units use the official `GebouwObjectId` relation. The public address
+collection does not expose that relation directly, so addresses are linked
+only through an exact, unambiguous unit position or unambiguous polygon
+containment. Ambiguous and unmatched rows are counted in the manifest and are
+never forced to the nearest building.
+
+The queryable layer contains building polygons, lifecycle status and aggregate
+unit/address counts only. Street names, full addresses, house numbers and box
+numbers are excluded. Address counts are not households, dwellings, residents
+or population. Raw source pages remain restricted operator evidence and are
+not exposed by the API or map.
+
+Official endpoints and catalogues:
+
+- https://geo.api.vlaanderen.be/Gebouwenregister/ogc/features/v1/collections/Gebouw/items
+- https://geo.api.vlaanderen.be/Gebouwenregister/ogc/features/v1/collections/Gebouweenheid/items
+- https://geo.api.vlaanderen.be/Adressenregister/ogc/features/v1/collections/Adres/items
+- https://www.vlaanderen.be/datavindplaats/catalogus/gebouwen-en-adressenregister
+- https://www.vlaanderen.be/datavindplaats/catalogus/gebouwenregister
+
+Digitaal Vlaanderen is transitioning the download products in summer 2026.
+This operator uses the current production OGC API and does not depend on the
+retiring `/v2/extract` path.
 
 ## Lokale demo datasets