Add fail-closed Belgian training loop

docs/CODEX_EXECUTION_LOG.md

@@ -11531,3 +11531,26 @@ Next gate:
   production gate, so it was not promoted. The active model remains unchanged.
   The deterministic audit status is `needs_human_review`: an AI-assisted visual
   inspection cannot be represented as the required human approval.
+
+## 2026-07-27 - Closed national training loop and corpus v3
+
+- Defined a fail-closed completion contract: calibration selects a threshold by
+  worst-region F1, while independent regional test and pure-empty background
+  sets decide completion. Passing requires aggregate F1 0.55, every region F1
+  0.45/precision 0.50/recall 0.40 and zero pure-empty detections.
+- Added deterministic per-AOI IoU matching and iteration assessment scripts.
+  Protected AOIs remain excluded from training and a failed assessment emits
+  `continue_training_loop` rather than a success-shaped result.
+- Expanded the governed portfolio from 42 to 60 AOIs: per region 10 train, two
+  validation, three calibration, three test and two background-test samples.
+  Frozen corpus `building-be-v3-20260727-r1` contains 10,262 accepted labels;
+  manifest SHA-256 is
+  `299212d1b3881330a6e3e936836d279435ab80c156a012121fe566ad0f3eae22`.
+- Corpus composition and spatial leakage pass. All 60 mosaics retain explicit
+  unknown per-pixel observation time; no download timestamp is used as a false
+  alignment claim.
+- The first 97-epoch loop candidate improved validation mAP50 to `0.250` and
+  mAP50-95 to `0.0835`, but the strict regional assessment failed, particularly
+  for Flanders and Wallonia, and recorded one pure-empty false positive at the
+  calibration-selected threshold. Training therefore continued on v3; no model
+  was promoted and human review remains intentionally deferred.