derive cleaner min-4px YOLO corpus

docs/TODO.md

@@ -1164,9 +1164,12 @@ This file now starts with the current implementation status. Older preparation/b
   sheets and retain immutable hashes.
 - [x] Reconstruct exact cross-tile interior objects and prove that overlap
   repeats 40,031 label rows but causes zero reconstructed train/val crossings.
-- [ ] Build the next immutable experimental corpus with `min_label_px >= 4`
-  and compare the existing 0.35 edge-visibility policy against a separately
-  versioned stricter ablation before any new governed training.
+- [x] Build and fully audit an immutable experimental corpus with
+  `min_label_px=4`; retain 252 tiles and 77,380 labels with zero sub-4-pixel
+  rows, missing files, invalid labels or cross-split reconstructed objects.
+- [ ] Compare the existing 0.35 edge-visibility policy against a separately
+  versioned stricter ablation from original source geometry before any new
+  governed training; do not approximate this by dropping every edge label.
 - [ ] Convert the AI-assisted ledger into no stronger claim than experimental
   triage; a real human must independently review and sign the frozen artifacts
   before the governed training wrapper may unlock.