feat: complete governed Walloon coverage sources

docs/DATA_COVERAGE_STATUS.md

@@ -26,7 +26,7 @@ coverage or historical dates.
 | --- | --- | --- |
 | Belgium | NGI administrative boundaries; Statbel population/statistical sectors | Statbel population 2021-2025 |
 | Flanders | GRB buildings, roads, water and parcels; DHMV terrain/surface; VMM flood scenarios; BWK/Natura 2000; DOV soil; policy rasters for space, open space, accessibility and services; agriculture and orthophoto where governed | Population 2021-2025; land-use/land-cover series where retained; agriculture editions; historical maps/orthophotos where the selected product has a real observation date |
-| Wallonia | Bounded PICC buildings, roads and hydrography; governed SPW bed-elevation/bathymetry products | No general cross-theme regional history yet |
+| Wallonia | Bounded PICC buildings, roads and hydrography; legal SPW flood-hazard polygons; bounded WALOUS 2020/2023 land-cover analysis from provisioned official rasters; governed SPW bed-elevation/bathymetry products | Comparable WALOUS land-cover area metrics for 2020-2023; no general cross-theme regional history yet |
 | Brussels | Bounded UrbIS buildings, street axes, cadastral parcels and Land Cover blocks; official FO/GB blocks provide forest/park area and WB blocks provide permanent water area | No general cross-theme regional history yet; the live WFS has no per-feature observation date |
 | Belgian North Sea | RBINS reporting units; Marine Spatial Plan 2026-2034; governed MDK bathymetry only when runtime acquisition is explicitly configured | No multi-epoch bathymetry or marine-plan trend yet |
 
@@ -37,23 +37,21 @@ applicable bounded official source or reports the theme as unsupported.
 
 ## Priority coverage gaps
 
-1. Govern the public Walloon WALOUS land-cover editions (including the
-   published 2018/2020 change product) as a real regional time series. A class
-   crosswalk is required because the older COSW 2005/2007 methodology differs.
-   Official catalogue:
-   `https://geoportail.wallonie.be/catalogue-donnees?search-text=occupation+du+sol`.
-2. Govern the current public Walloon flood-hazard vector/raster products and
-   retain their model scenario semantics separately from observed floods.
-   Official record:
-   `https://geoportail.wallonie.be/catalogue/14084108-2c7b-4091-b62d-ff0fc235213a.html`.
-3. Add a common Belgium-wide topographic baseline with normalized theme
+1. Add the official WALOUS 2018 edition only after SPW restores a stable direct
+   artifact or another checksum-verifiable acquisition contract. WALOUS 2020
+   and 2023 are operational and comparable; COSW 2005/2007 remains a different
+   methodology and is not silently merged.
+2. Add a common Belgium-wide topographic baseline with normalized theme
    semantics across NGI, Flanders, Wallonia and Brussels.
-4. Govern comparable Walloon and Brussels historical editions before exposing
+3. Govern comparable Walloon and Brussels historical editions before exposing
    evolution for buildings, roads, land cover, soil, elevation or flood risk.
-5. Add nationally comparable land-cover history with explicit class crosswalks
+4. Add nationally comparable land-cover history with explicit class crosswalks
    and uncertainty; never compare incompatible legends silently.
-6. Add multi-epoch marine bathymetry and survey-footprint metadata before
+5. Add multi-epoch marine bathymetry and survey-footprint metadata before
    presenting seabed evolution.
+6. Add Walloon DTM only through an operator capacity plan: the official 1 m
+   national artifact is about 41 GB and the 0.5 m artifact about 213 GB, so it
+   is not safe as an implicit per-selection dependency.
 7. Expand persisted raster partition manifests beyond the regression regions
    only where repeated use justifies caching; bounded acquisition remains the
    default for one-off selections.