Use split background reports in promotion gate

scripts/README.md

@@ -679,6 +679,26 @@ and maximum background detections per sample. It is evidence/report tooling
 only: it does not run inference, mutate application data, download models or
 change the active YOLO configuration.
 
+When the background corpus has been split with
+`run_background_corpus_split_matrix.sh`, pass the combined split summary instead
+of manually wiring both category summaries:
+
+```bash
+python scripts/build_detection_model_promotion_report.py \
+  --positive-portfolio /mnt/user/appdata/geointel/artifacts/detection-quality-matrix/multi-sample/aoi1024bg512r3e50-positive/multi_sample_quality_summary.json \
+  --background-split-summary /mnt/user/appdata/geointel/artifacts/detection-hard-negatives/aoi1024bg512r3e50-split/background_corpus_split_summary.json \
+  --output-dir /mnt/user/appdata/geointel/artifacts/detection-model-promotion/aoi1024bg512r3e50-split-aware \
+  --min-positive-samples 7 \
+  --min-background-samples 2 \
+  --min-mean-f1 0.25 \
+  --max-background-detections-per-sample 0
+```
+
+The promotion report resolves the split summary's `pure_empty_negative` source
+summary as the strict default-promotion false-positive gate. The
+`sparse_building_context` source remains visible in the JSON/Markdown report as
+review evidence only and is not counted as a default-promotion gate.
+
 If a legacy positive evidence portfolio records `model_asset_id` at portfolio
 level but does not include per-run tile size/overlap, pass explicit tile
 defaults instead of letting the report guess: