chore(experiments): X-Ray rerun and opencv5 dump runners

- run_xray_lvface_opencv5.sh: end-to-end X-Ray benchmark (scene_analyze
  per film → sample_eval) on the current build with LVFace-B.
- dump_lvface_opencv5.sh: fresh LVFace-B embedding dumps (plain front-half,
  histogram cuts baked in) for the optimizer replay corpus. No decode-fps
  cap — that only mattered under parallel dumping; serial it just halved
  throughput.
- .gitignore: ignore build-*/ out-of-tree build dirs.

experiments/run_xray_lvface_opencv5.sh

@@ -0,0 +1,60 @@
+#!/usr/bin/env bash
+# Re-benchmark the feature/opencv5 pipeline against Amazon X-Ray, all 9 films, LVFace-B.
+# Full end-to-end scene_analyze (decode→detect→scene→embed→match→presence) — NOT a replay,
+# because the framework changed enough that old embedding dumps no longer represent the front half.
+# Outputs land in experiments/results/xray_opencv5_lvface/ (durable; /tmp gets wiped).
+set -uo pipefail
+
+REPO="/home/dtourolle/Development/scene-actor-extraction"
+cd "$REPO"
+
+ARC="models/LVFace-B_Glint360K.onnx"
+GAL="experiments/galleries/gallery_LVFace-B_Glint360K.h5"
+OUT="experiments/results/xray_opencv5_lvface"
+mkdir -p "$OUT"
+
+BIN="build/scene_analyze"
+LUT="experiments/file-lut.json"
+FILMS="experiments/manifests/films.json"
+
+# film slugs and their xray dirs, from films.json
+mapfile -t ROWS < <(python3 -c '
+import json
+for f in json.load(open("'"$FILMS"'")):
+    print(f["slug"] + "\t" + f["xray"])
+')
+
+echo "=== X-Ray re-benchmark (feature/opencv5, LVFace-B) — $(date) ===" | tee "$OUT/run.log"
+
+for row in "${ROWS[@]}"; do
+    slug="${row%%$'\t'*}"
+    xray="${row#*$'\t'}"
+    movie="$(python3 -c 'import json,sys; print(json.load(open("'"$LUT"'"))["'"$slug"'"])')"
+    pred="$OUT/${slug}.json"
+
+    echo "" | tee -a "$OUT/run.log"
+    echo ">>> $slug" | tee -a "$OUT/run.log"
+    if [ ! -f "$movie" ]; then
+        echo "  SKIP: movie missing: $movie" | tee -a "$OUT/run.log"
+        continue
+    fi
+
+    # Run the full pipeline (serial — ROCm GPU wedges at concurrency>2-3).
+    "$BIN" --movie "$movie" --arcface "$ARC" --gallery "$GAL" \
+        --output "$pred" >"$OUT/${slug}.pipeline.log" 2>&1
+    rc=$?
+    if [ $rc -ne 0 ] || [ ! -f "$pred" ]; then
+        echo "  PIPELINE FAILED (rc=$rc) — see ${slug}.pipeline.log" | tee -a "$OUT/run.log"
+        continue
+    fi
+    echo "  pipeline ok" | tee -a "$OUT/run.log"
+
+    # Score against X-Ray, masked to gallery∩GT, 1s grid.
+    python scripts/validation/sample_eval.py \
+        --pred "$pred" --xray "$xray" --gallery "$GAL" --step 1.0 \
+        >"$OUT/${slug}.eval.txt" 2>&1
+    tail -8 "$OUT/${slug}.eval.txt" | tee -a "$OUT/run.log"
+done
+
+echo "" | tee -a "$OUT/run.log"
+echo "=== DONE — $(date) ===" | tee -a "$OUT/run.log"