Add SUM Parts reproduction and Seosan Myeongcheon application pipeline

Reproduces the SUM Parts (CVPR 2025) face-labeling benchmark on a single
consumer GPU, then applies it to drone-photogrammetry road survey meshes.

Verified on RTX 3060 12GB / WSL2 Ubuntu 22.04 / CUDA 11.8 / torch 2.0.1:
- CUDA extensions build (pointnet2_batch, pointops, chamfer_dist, emd,
  subsampling)
- PointNet 100 epochs reaches mIoU 17.19, matching the paper's reported 15.1
- OBJ -> PLY conversion round-trips through the model and yields per-point
  predictions

Four upstream source patches, all idempotent, originals preserved:
- numpy aliases removed in 1.24 (np.long etc.) and collections ABCs moved in
  python 3.10
- the blind test split ships label = -1, which crashed ConfusionMatrix
- mode=val referenced `epoch` before assignment

Documents the traps that cost the most time, including VRAM overflow silently
falling back to host RAM on WSL2 (25-100x slowdown, no OOM) and the colour
scale mismatch between r/g/b float32 and red/green/blue uint8.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/list_archive.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# SUM Parts - list an archive's contents without extracting it
+#
+# Used to count tiles per split, which is what turns a per-iteration benchmark
+# into a wall-clock training estimate.
+set -euo pipefail
+
+ARCHIVE="${1:-$HOME/sum-parts/data/_archives/mesh.zip}"
+
+source "$HOME/miniconda3/etc/profile.d/conda.sh"
+conda activate sumparts
+
+python - "$ARCHIVE" <<'PY'
+import re
+import sys
+import zipfile
+from collections import Counter
+from pathlib import Path
+
+path = Path(sys.argv[1])
+z = zipfile.ZipFile(path)
+names = z.namelist()
+
+print(f"=== {path.name} : {len(names)} entries ===\n")
+
+dirs = Counter()
+for n in names:
+    p = "/".join(n.split("/")[:-1]) or "."
+    dirs[p] += 1
+for d, c in sorted(dirs.items()):
+    print(f"  {c:>5}  {d}/")
+
+print()
+splits = Counter()
+for n in names:
+    m = re.search(r"(?:^|/)(train|val|test|training|validation)(?:/|_)", n, re.I)
+    if m:
+        splits[m.group(1).lower()] += 1
+if splits:
+    print("split hints:", dict(splits))
+
+ply = [n for n in names if n.lower().endswith(".ply")]
+print(f"\n.ply entries: {len(ply)}")
+
+per_split = Counter(n.split("/")[0] for n in ply)
+for s, c in sorted(per_split.items()):
+    print(f"   {c:>4} ply  in {s}/")
+
+for n in ply[:5]:
+    print(f"   e.g. {n}")
+
+total = sum(i.file_size for i in z.infolist())
+print(f"\nuncompressed total: {total / 1e9:.2f} GB")
+PY