correct overlapping checkpoint evaluation

docs/CODEX_EXECUTION_LOG.md

@@ -12671,3 +12671,36 @@ Open:
 - The min-4px corpus is preferred for future experimental work, but remains
   explicitly training/release-ineligible until real human review and governed
   release evidence exist. The active GPU model was not changed.
+
+## 2026-08-09 - Non-overlapping checkpoint correction
+
+### Corrected
+
+- Traced the prior 36-image checkpoint matrix to four AOIs tiled at 512/256.
+  The same interiors were repeated and nine Arendonk-heide tiles were visually
+  blank no-data, despite being counted as background observations.
+- Added a deterministic non-overlap evaluation-view builder. It selects four
+  complete 512 px grid tiles per 1024 px AOI, excludes low-variance no-data
+  with reason codes, creates empty train directories and writes a hashed
+  `NO_TRAINING.json` marker.
+- Added a fail-fast marker check to the operator YOLO training wrapper before
+  release verification, model loading or CUDA allocation.
+- Corrected checkpoint overlap semantics: zero pixel overlap is reported, but
+  statistical independence is explicitly not established for adjacent tiles.
+
+### GPU evidence
+
+- The clean r2 view contains 12 images: eight positive Turnhout/Westerlo tiles
+  and four real Postel backgrounds. It has 2,551 labels, 2,384 unique interior
+  objects, 167 edge labels and zero repeated interior objects.
+- Active: precision 0.542632, recall 0.435317, mAP50 0.342034, mAP50-95
+  0.141316. Challenger: 0.581715, 0.462300, 0.368364 and 0.155318.
+- At confidence 0.15 the active model has zero Postel detections and the
+  challenger one; at 0.25 both have zero. The threshold-sensitive relative
+  challenger advantage is confirmed without changing production.
+
+### Remaining limitations
+
+- Two adjacent positive AOIs and one real background AOI are not representative
+  release evidence. Human review, broader independent geography and exact
+  challenger provenance remain blocking.