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/RunL116HashMatrix.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""Compare the L116 hash matrix directly with the saved L115 matrix."""
+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/hashes"
+BASE = ROOT / "Saved/Linux/l115/hashes"
+DATASETS = {
+    "owner4": ROOT / "Standalone/data/owner_world.json",
+    "owner2": ROOT / "Standalone/data/regression/owner_world_2strate_l61.json",
+}
+BINARIES = {
+    "clang": ROOT / "Saved/Linux/l116/bin/VoxelForgeCoreHeadless-l116-clang",
+    "gcc": ROOT / "Saved/Linux/l116/bin/VoxelForgeCoreHeadless-l116-gcc",
+}
+HASH = re.compile(r"^\[Pipeline(?:FullDetailHash|WholeViewHash|LODHash|ExactQueryHash)\].*$", re.M)
+STAMP = re.compile(r"^\[VoxelForgeSourceStamp\] sha256=(\S+)$", re.M)
+
+
+def run(dataset: str, recipe: str, workers: int, compiler: str) -> dict:
+    OUT.mkdir(parents=True, exist_ok=True)
+    label = f"{dataset}-{recipe}-w{workers}-{compiler}"
+    log = OUT / f"{label}.log"
+    layout = OUT / f"{label}.layout.json"
+    command = [
+        "taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--",
+        "timeout", "1740s", str(BINARIES[compiler]), str(DATASETS[dataset]),
+        f"--workers={workers}", "--world-assembler-prototype", "--stream-benchmark",
+        "--stream-pipeline", "--force-generate", "--clip-radius=3",
+        "--max-clip-level=8", "--max-level=8", f"--recipe={recipe}",
+        "--stream-hash", f"--resolved-layout-output={layout}",
+    ]
+    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)
+    output = log.read_text(encoding="utf-8", errors="replace")
+    hashes = HASH.findall(output)
+    baseline_log = BASE / f"{label}.log"
+    baseline_hashes = HASH.findall(baseline_log.read_text(encoding="utf-8", errors="replace"))
+    if result.returncode or len(hashes) != 12 or hashes != baseline_hashes:
+        raise SystemExit(f"hash mismatch or incomplete run: {label}; exit={result.returncode} "
+                         f"l116={len(hashes)} l115={len(baseline_hashes)} log={log}")
+    row = {
+        "dataset": dataset, "recipe": recipe, "workers": workers,
+        "compiler": compiler, "exit_code": result.returncode,
+        "matches_l115": True, "hashes": hashes,
+        "source_stamp": (STAMP.search(output).group(1) if STAMP.search(output) else None),
+        "elapsed_s": round(time.monotonic() - started, 3),
+        "log": str(log.relative_to(ROOT)),
+        "l115_log": str(baseline_log.relative_to(ROOT)),
+    }
+    print("[L116HashRun] " + json.dumps(row, sort_keys=True), flush=True)
+    return row
+
+
+def main() -> int:
+    if any(not path.is_file() for path in (*DATASETS.values(), *BINARIES.values())):
+        raise SystemExit("missing L116 hash input")
+    rows = []
+    recipes = {"owner4": ("surface-world",),
+               "owner2": ("surface-world", "floating-islands")}
+    for dataset, dataset_recipes in recipes.items():
+        for recipe in dataset_recipes:
+            for workers in (1, 8, 12):
+                for compiler in ("clang", "gcc"):
+                    rows.append(run(dataset, recipe, workers, compiler))
+                    (OUT / "runs-partial.json").write_text(
+                        json.dumps(rows, indent=2) + "\n", encoding="utf-8")
+    summary = {
+        "runs": rows,
+        "all_hashes_match_l115": all(row["matches_l115"] for row in rows),
+        "owner4_all_four_strata": "owner4/surface-world",
+        "worker_counts": [1, 8, 12],
+        "compilers": ["clang", "gcc"],
+    }
+    (OUT / "summary.json").write_text(json.dumps(summary, indent=2) + "\n",
+                                      encoding="utf-8")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())