research: chord-bound + z-column fine-segment pruning (L116, exact, not merged)

Fine pairs 48.9M -> 38.8M (-21%) with L115-identical hashes, but no readiness change (still
+15..+30% near-ready vs L109). Pair evaluation is not where the regression lives. Kept as patch.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Research/WorldAssemblerM3/Linux116/RunL116PairCounts.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python3
+"""Count exact fine-segment/sample evaluations in the four L80 views."""
+from __future__ import annotations
+
+import json
+import re
+import subprocess
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[4]
+OUT = ROOT / "Saved/Linux/l116/pairs"
+DATA = ROOT / "Standalone/data/owner_world.json"
+BIN = ROOT / "Saved/Linux/l116/bin/VoxelForgeCoreHeadless-l116-clang"
+CAMERAS = {
+    0: (8.0, 16.0, -372.2626953125),
+    1: (25.8369140625, 3.19921875, -737.0),
+    2: (19.166015625, -14.2001953125, -753.3740234375),
+    3: (-20.0625, -5.068359375, -900.353515625),
+}
+PAIRS = re.compile(r"\bsweep_pairs=(\d+)")
+
+
+def run(strate: int) -> dict:
+    OUT.mkdir(parents=True, exist_ok=True)
+    log = OUT / f"L116-s{strate}.log"
+    camera = ",".join(f"{v:.12f}" for v in CAMERAS[strate]) + ",0,0"
+    command = [
+        "taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--",
+        "timeout", "1740s", str(BIN), str(DATA),
+        "--world-assembler-prototype", "--stream-benchmark", "--stream-pipeline",
+        "--workers=12", "--clip-radius=3", "--max-clip-level=8", "--max-level=8",
+        f"--camera={camera}", "--profile-passage-composer",
+        "--stream-scheduler-policy=3",
+    ]
+    started = time.monotonic()
+    with log.open("w", encoding="utf-8") as stream:
+        result = subprocess.run(command, cwd=ROOT, stdout=stream,
+                                stderr=subprocess.STDOUT, check=False, timeout=1740)
+    values = [int(value) for value in PAIRS.findall(
+        log.read_text(encoding="utf-8", errors="replace"))]
+    if result.returncode or not values:
+        raise SystemExit(f"pair profile missing: {log}; exit={result.returncode}")
+    row = {"strate": strate, "tiles": len(values), "segment_sample_pairs": sum(values),
+           "elapsed_s": round(time.monotonic() - started, 3),
+           "log": str(log.relative_to(ROOT))}
+    print("[L116PairCount] " + json.dumps(row, sort_keys=True), flush=True)
+    return row
+
+
+def main() -> int:
+    if not BIN.is_file() or not DATA.is_file():
+        raise SystemExit("missing L116 pair-count input")
+    rows = [run(strate) for strate in range(4)]
+    summary = {"strata": rows,
+               "total_segment_sample_pairs": sum(row["segment_sample_pairs"]
+                                                  for row in rows)}
+    (OUT / "summary.json").write_text(json.dumps(summary, indent=2) + "\n",
+                                      encoding="utf-8")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())