Suppress duplicate YOLO tile detections

docs/API_CONTRACTS.md

@@ -785,6 +785,12 @@ Validation errors:
 - Configured YOLO inference forwards `YOLO_MAX_DETECTIONS` to Ultralytics
   `max_det` and defaults to `1000` so dense building AOIs are not silently
   limited by the upstream default of 300 detections before persisted QA/QC.
+- Configured YOLO applies cross-tile duplicate suppression after pixel boxes are
+  converted to EPSG:4326 geometries and before `Detection` rows are persisted.
+  Same-class candidates are confidence-sorted and lower-confidence candidates
+  with geometry IoU greater than or equal to
+  `YOLO_DUPLICATE_IOU_THRESHOLD` are suppressed. The default is `0.5`; `0`
+  disables this GeoIntel-side post-processing for debugging.
 - `DETECTION_DEPENDENCY_UNAVAILABLE` when YOLO dependencies are not installed.
 - `DETECTION_MODEL_LOAD_FAILED` when the local model file exists but cannot be loaded.