fix: close Walloon terrain provisioning

docs/CODEX_EXECUTION_LOG.md

@@ -11173,3 +11173,36 @@ Known governed boundaries remain explicit: WALOUS covers Wallonia rather than
 all Belgium, no unstable 2018 artifact is accepted without a verifiable source
 checksum, and the current local building model is not represented as nationally
 trained or validated.
+
+## 2026-07-22 - WALOUS 2018, Walloon terrain and evidence-scope closure
+
+Implemented and verified:
+
+- accepted the stable official WALOUS 2018 distribution only after validating
+  the 1,122,785,133-byte archive (`21e514...c9a`) and extracted raster
+  (`a788cf...56b2`), then materialized one area-scoped 2018/2020/2023 series;
+- exposed that governed series in the evolution workspace and removed foreign
+  Area acquisitions from its choices; the live Wallonia golden Area shows
+  exactly three official moments and one unambiguous series;
+- provisioned the complete official SPW MNT 2021-2022 1 m source. The archive
+  was 43,904,242,006 bytes with SHA-256 `04f3ca45821dc2866d854e75011eed1acefcfead9a5263e5a9760e29ded21f7c`;
+  the extracted EPSG:3812 Float32 raster is 44,014,505,895 bytes, 253,085 by
+  146,727 cells, uses nodata -9999 and SHA-256
+  `027f90fd304b683cdbf9a0c735152769cf093eb38599e7d5d9dc8792040a9f61`;
+- removed the 40.89 GiB terrain download archive after checksum validation and
+  retained the source raster, checksum sidecar and atomic provisioning report;
+- made terrain availability fail closed until both raster and valid SHA-256
+  sidecar exist, and persisted the official 2021-02-19/2022-03-05 observation
+  interval using the canonical `period` granularity;
+- constrained AI capability claims to the actual Mol/Kempen evidence through
+  machine-readable training/validation scope, `nationally_validated=false` and
+  mandatory operator review. No national training result was fabricated.
+
+Pre-release evidence:
+
+- the complete readiness gate passed with 1,103 backend tests and 34 frontend
+  tests, backend compile, API/documentation contract audit, frontend typecheck,
+  production build, Alembic head `202607160001` and all script checks;
+- live browser acceptance showed the exact WALOUS 2018-2023 series and no
+  console warnings or errors. Final terrain Dataset and immutable-image evidence
+  are recorded after deployment below.