research: region completion gate (L123, no production change)

The 18 ms gate is one game-thread tick, not compile cost (0.25 ms). MPSC handoff keeps ownership but still
polls per tick; velocity look-ahead didn't help (near -0.8 pt, p99 11.77 > 11.00). Both kept as a patch.

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

Standalone/Research/WorldAssemblerM3/Linux123/RunL123Headless.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""One 30 m/s headless movement run for the UE-only region gate experiment."""
+from __future__ import annotations
+
+import json
+import math
+import re
+import subprocess
+import time
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[4]
+DATA = ROOT / "Standalone/data/owner_world.json"
+BIN = ROOT / "Saved/Linux/l108/bin/VoxelForgeCoreHeadless-l108-after-clang"
+OUT = ROOT / "Saved/Linux/l123/headless"
+SAMPLE = re.compile(r"^\[L79MovingSample\] (.*)$", re.M)
+SUMMARY = re.compile(r"^\[L79MovingSummary\] (.*)$", re.M)
+FIELDS = re.compile(r"([a-zA-Z0-9_]+)=([^ ]+)")
+
+
+def p99(values: list[float]) -> float | None:
+    if not values:
+        return None
+    values.sort()
+    return values[max(0, math.ceil(0.99 * len(values)) - 1)]
+
+
+def main() -> int:
+    OUT.mkdir(parents=True, exist_ok=True)
+    log = OUT / "movement-30mps-r1.log"
+    camera = "19.166015625000,-14.200195312500,-753.374023437500,0,0"
+    command = [
+        "taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--",
+        "timeout", "1740s", str(BIN), str(DATA), "--world-assembler-prototype",
+        "--stream-benchmark", "--stream-pipeline", "--workers=8", "--clip-radius=3",
+        "--max-clip-level=8", "--max-level=8", f"--camera={camera}",
+        "--profile-lod-work", "--stream-scheduler-policy=3",
+        "--moving-camera-speed-mps=30.0", "--moving-camera-duration-s=12",
+        "--moving-camera-dwell-s=5",
+    ]
+    started = time.monotonic()
+    with log.open("w", encoding="utf-8") as stream:
+        process = subprocess.run(command, cwd=ROOT, stdout=stream,
+                                 stderr=subprocess.STDOUT, check=False, timeout=1740)
+    content = log.read_text(encoding="utf-8", errors="replace")
+    rows = []
+    for match in SAMPLE.finditer(content):
+        row = dict(FIELDS.findall(match.group(1)))
+        for name in ("near_ready_pct", "far_hole_pct", "queue_update_ms"):
+            if name in row:
+                row[name] = float(row[name])
+        row["phase"] = row.get("phase", "move")
+        rows.append(row)
+    summary = dict(FIELDS.findall(SUMMARY.search(content).group(1))) if SUMMARY.search(content) else {}
+    moving = [row for row in rows if row["phase"] == "move"]
+    updates = [row["queue_update_ms"] for row in moving if "queue_update_ms" in row]
+    result = {
+        "exit_code": process.returncode,
+        "wall_s": round(time.monotonic() - started, 3),
+        "moving_samples": len(moving),
+        "near_ready_moving_mean_pct": sum(r["near_ready_pct"] for r in moving) / max(1, len(moving)),
+        "far_holes_moving_mean_pct": sum(r["far_hole_pct"] for r in moving) / max(1, len(moving)),
+        "update_work_p99_ms": p99(updates),
+        "update_work_max_ms": max(updates, default=None),
+        "generation_failures": int(summary.get("generation_failures", -1)),
+        "log": str(log.relative_to(ROOT)),
+    }
+    (OUT / "summary.json").write_text(json.dumps(result, indent=2) + "\n",
+                                       encoding="utf-8")
+    print("[L123Headless] " + json.dumps(result, sort_keys=True), flush=True)
+    if process.returncode or not moving or result["generation_failures"] != 0:
+        return 1
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())