core: A/A noise floor (±1%) and small hot-path trims for the cave planner (L137, output = v236)

Identical builds differ <=0.6% median; residual near-ready vs assembler/world is real: Surface World +2.9..+3.6%,
Vertical Shafts +4.0..+4.3%, Tunnel Network -3.6/+6.8%. Profile points at column-cache reads and the sweep lookup.
Removed an unused sample field and per-lookup shared_ptr refcounting. 16/16 seeds, fast tier, Clang/GCC green.

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

Standalone/Research/WorldAssemblerM3/Linux137/RunL137SeedSweep.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+"""Run the L137 composed passage and tile-seam audits for seeds 0 through 15."""
+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/l137/seeds"
+BIN = ROOT / "Saved/Linux/l137/fast/bin/VoxelForgeCoreHeadless-fast-clang"
+DATA = ROOT / "Standalone/data/owner_world.json"
+STAMP = "dcf2ffa55fd6d62b3c7faf76229c3b99c635868dc1b694fc6e8f39e738775a4e"
+STAMP_RE = re.compile(r"^\[VoxelForgeSourceStamp\] sha256=([0-9a-f]+)$", re.M)
+REQUIRED = {
+    "passage": re.compile(r"^\[ResolvedPassageAuditSummary\].*status=PASS$", re.M),
+    "seams": re.compile(r"^\[PassageTileSeamAudit\].*status=PASS$", re.M),
+    "shell": re.compile(r"^\[PassageShellAuditSummary\].*status=PASS$", re.M),
+    "naturalness": re.compile(r"^\[PassageNaturalnessSummary\].*status=PASS$", re.M),
+    "mouth_profile": re.compile(r"^\[PassageMouthProfileSummary\].*status=PASS$", re.M),
+    "ripple": re.compile(r"^\[PassageRippleAuditSummary\].*status=PASS$", re.M),
+    "route_negative_control": re.compile(
+        r"^\[TunnelNetworkBlockedRouteControl\].*expected=FAIL status=PASS$", re.M),
+}
+
+
+def main() -> int:
+    if not BIN.is_file() or not DATA.is_file():
+        raise SystemExit("missing L137 fast binary or owner fixture")
+    OUT.mkdir(parents=True, exist_ok=True)
+    results = []
+    for seed in range(16):
+        log = OUT / f"seed{seed}.log"
+        layout = OUT / f"seed{seed}.json"
+        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=0",
+            "--force-generate", f"--seed={seed}", "--recipe=surface-world",
+            "--audit-resolved-layout-passages", "--audit-passage-tile-seams",
+            f"--resolved-layout-output={layout}"]
+        started = time.monotonic()
+        with log.open("w", encoding="utf-8") as output:
+            result = subprocess.run(command, cwd=ROOT, stdout=output,
+                                    stderr=subprocess.STDOUT, check=False, timeout=1740)
+        content = log.read_text(encoding="utf-8", errors="replace")
+        found_stamp = STAMP_RE.search(content)
+        checks = {name: bool(pattern.search(content)) for name, pattern in REQUIRED.items()}
+        checks["source_stamp"] = found_stamp is not None and found_stamp.group(1) == STAMP
+        blocked = re.findall(r"^\[ResolvedPassageBlockedControl\].*detected=true$",
+                             content, re.M)
+        checks["three_blocked_controls"] = len(blocked) == 3
+        passed = result.returncode == 0 and all(checks.values())
+        row = {"seed": seed, "exit": result.returncode, "passed": passed,
+               "checks": checks, "blocked_controls": len(blocked),
+               "elapsed_s": round(time.monotonic() - started, 3),
+               "log": str(log.relative_to(ROOT)), "layout": str(layout.relative_to(ROOT))}
+        results.append(row)
+        print("[L137SeedSweep] " + json.dumps(row, sort_keys=True), flush=True)
+        (OUT / "runs-partial.json").write_text(json.dumps(results, indent=2) + "\n")
+        if not passed:
+            raise SystemExit(f"seed {seed} failed composed audits; see {log}")
+    summary = {"source_stamp": STAMP, "seeds": list(range(16)),
+               "passed": len(results), "failed": 0, "results": results}
+    (OUT / "summary.json").write_text(json.dumps(summary, indent=2) + "\n")
+    print("[L137SeedSweepSummary] passed=16/16 status=PASS")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())