derive cleaner min-4px YOLO corpus

docs/CODEX_EXECUTION_LOG.md

@@ -12638,3 +12638,36 @@ Open:
   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.
+
+## 2026-08-09 - Immutable min-4px derived corpus
+
+### Improved
+
+- Added a deterministic derived-corpus builder that preserves parent hashes,
+  copies imagery, records every removed source row and refuses to turn a
+  positive tile into an unlabeled negative. It creates no release manifest or
+  human-review claim.
+- Derived `yolo-building-aoi1024-reviewedexp6-minpx4-derived-r1` from the
+  frozen min-3px corpus. Exactly 1,812 marginal labels were removed; all 252
+  tiles and 77,380 labels remain, with zero excluded tiles.
+- Corrected the quality-audit console message from `passed` to `completed`, so
+  a machine-readable `needs_attention` status is no longer contradicted by
+  human-facing output.
+
+### Verified on Tower
+
+- Structural audit: zero missing/invalid labels and zero sub-4-pixel rows.
+- Relationship audit: zero exact/near duplicates and 41 possible nesting
+  pairs, down from 43.
+- Geometry audit: 10 plausible extreme-aspect rows, down from 26; tile-edge
+  rows fell from 5,079 to 4,840 without a blanket edge deletion.
+- Cross-tile audit: zero reconstructed train/validation crossings.
+- Inspected four full contact-sheet pages covering all 252 tiles and 77,380
+  labels plus the focused nine-tile extreme-aspect sheet. Pure backgrounds
+  remain empty and sparse contexts remain distinct.
+
+### Decision and limitation
+
+- 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.