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/dump_lvface_opencv5.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# Fresh LVFace-B embedding dumps (HDF5) for all 9 X-Ray films with the current
+# feature/opencv5 build, for the flood-fill GA optimisation. Plain front-half
+# (decode -> campos -> detect -> align -> embed); no scene detection (histogram
+# cuts is_cut are baked in for flood-fill). Hardware VAAPI decode, no MIGraphX,
+# no crash. Serial -- ROCm GPU wedges at concurrency>2-3.
+set -uo pipefail
+
+REPO="/home/dtourolle/Development/scene-actor-extraction"
+cd "$REPO"
+
+ARC="models/LVFace-B_Glint360K.onnx"
+BIN="build/dump_embeddings"
+LUT="experiments/file-lut.json"
+FILMS="experiments/manifests/films.json"
+OUT="experiments/dumps/LVFace-B_Glint360K_opencv5"
+mkdir -p "$OUT"
+
+# Persist MIOpen tuning so SCRFD/ArcFace kernel search is paid once, not per film.
+export MIOPEN_USER_DB_PATH="$HOME/.cache/miopen-sae"
+export MIOPEN_FIND_MODE=NORMAL
+mkdir -p "$MIOPEN_USER_DB_PATH"
+
+mapfile -t SLUGS < <(python3 -c 'import json;[print(f["slug"]) for f in json.load(open("'"$FILMS"'"))]')
+
+echo "=== LVFace-B dumps (feature/opencv5) — $(date) ===" | tee "$OUT/dump.log"
+for slug in "${SLUGS[@]}"; do
+    movie="$(python3 -c 'import json;print(json.load(open("'"$LUT"'"))["'"$slug"'"])')"
+    out="$OUT/dump_${slug}.h5"
+    echo "" | tee -a "$OUT/dump.log"
+    echo ">>> $slug" | tee -a "$OUT/dump.log"
+    if [ -f "$out" ]; then echo "  exists, skip" | tee -a "$OUT/dump.log"; continue; fi
+    if [ ! -f "$movie" ]; then echo "  SKIP missing: $movie" | tee -a "$OUT/dump.log"; continue; fi
+    # No --max-decode-fps cap: that cap existed only to stop LVFace dump truncation
+    # under PARALLEL load (3 concurrent dumps). This runner is serial, so the cap
+    # just halved throughput for nothing — measured 54s vs 27s per 300s of film,
+    # identical face counts. Uncapped ~9 min/film vs ~18 min capped.
+    "$BIN" --movie "$movie" --arcface "$ARC" --out "$out" --fps 1 \
+        >"$OUT/${slug}.log" 2>&1
+    rc=$?
+    if [ $rc -ne 0 ] || [ ! -f "$out" ]; then
+        echo "  DUMP FAILED (rc=$rc) — see ${slug}.log" | tee -a "$OUT/dump.log"
+    else
+        stats=$(python3 -c 'import h5py,sys
+f=h5py.File(sys.argv[1])
+n=f["frames/timestamp_sec"].shape[0]
+faces=f["faces/embedding"].shape[0]
+cuts=int(f["frames/is_cut"][:].sum())
+print(f"frames={n} faces={faces} cuts={cuts}")' "$out" 2>/dev/null)
+        echo "  ok ($(du -h "$out" | cut -f1), $stats)" | tee -a "$OUT/dump.log"
+    fi
+done
+echo "" | tee -a "$OUT/dump.log"
+echo "=== DONE — $(date) ===" | tee -a "$OUT/dump.log"