audit YOLO geometry and overlapping validation rows

docs/CODEX_EXECUTION_LOG.md

@@ -12595,3 +12595,46 @@ Open:
 - This is explicit AI-assisted triage, not human adjudication. It improves the
   evidence and review precision but does not unlock governed production
   training or checkpoint promotion.
+
+## 2026-08-09 - Row-level geometry and cross-tile independence audit
+
+### Improved
+
+- Added a reproducible, read-only label-row auditor for sub-threshold pixel
+  dimensions, extreme aspect ratios and tile-edge clipping, with separate
+  category manifests accepted directly by the visual QA renderer.
+- Extended the renderer with orange extreme-aspect, blue small-dimension and
+  green tile-edge highlighting while preserving the existing duplicate/nesting
+  colors and source row indices.
+- Added an exact cross-tile repetition auditor that reconstructs global pixel
+  boxes from the exporter's `_r<row>_c<column>` offsets. Edge-clipped rows stay
+  explicitly unlinked rather than being guessed back to source objects.
+- Made checkpoint-matrix output disclose dataset tile overlap and explicitly
+  state whether validation rows are independent whenever a dataset summary is
+  available.
+
+### Tower findings
+
+- Reviewed all 79,192 rows: 1,812 have a dimension below 4 px, 26 have aspect
+  ratio at least 8 and 5,079 touch a tile edge; 6,657 unique rows are involved.
+- Inspected the complete 23-tile extreme sheet, all four small-dimension pages
+  covering 198 tiles, and a 64-tile edge sample. Most extreme shapes are valid
+  elongated structures, but 16 of 26 also fall below the 4 px floor.
+- Reconstructed 34,082 unique interior objects from 74,113 interior label rows.
+  Tile overlap adds 40,031 exact repeated rows across 24,701 object groups,
+  with maximum repetition four and zero cross-split groups.
+- Froze the next-corpus decision: restore `min_label_px >= 4`; test any stricter
+  edge-visible ratio as a separate immutable ablation rather than modifying
+  this corpus in place.
+
+### Verified
+
+- Focused auditor, renderer and checkpoint-evidence suite: 18 tests passed.
+- Scoped Ruff check, format check and Git whitespace check passed.
+
+### Remaining limitations
+
+- Existing overlapping-tile mAP is valid for relative non-protected ranking,
+  not independent object-level accuracy. A future benchmark must aggregate or
+  deduplicate objects before uncertainty claims.
+- No source label, frozen dataset, model weight or live runtime was changed.