wip(assembler): round L37 -- FI mouth carve-fade fix, no raised bridge (style 0); research R1

The passage mouth fade multiplied the signed carve distance by zero, which turned native rock into an
open surface (the reason earlier rounds stamped walk pads at mouths); it now blends between the
uncarved field and the full signed carve. The FI style-0 route followed a lifted grade envelope over
the crater (the "bridge"); it now runs on the rim and follows the native surface. New built-shape and
crease audits with thresholds frozen before the fix (L36 and box controls fail). 24/24 passage rows,
30/30 determinism, 16/16 invariants, 18/18 interface/ring. Unreal: one recipe setter (uncompiled).
Research R1 (read-only, web): ranked proposals for natural walkable mouths, floor-limited carve first.

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

Standalone/Research/WorldAssemblerM3/Linux37/RunLegacyAuditsL37.py

@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+"""Run the L13 route parity and L9 uniform-block proof audits on L37."""
+import re
+import subprocess
+import time
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[4]
+OUT = ROOT / "Saved/Linux/l37"
+BINARIES = {
+    "clang": OUT / "bin/VoxelForgeCoreHeadless-l37-final-clang",
+    "gcc": OUT / "bin/VoxelForgeCoreHeadless-l37-final-gcc",
+}
+RECIPES = ("floating-islands", "surface-world")
+rows = []
+failed = False
+
+for recipe in RECIPES:
+    for compiler, binary in BINARIES.items():
+        name = f"legacy-route-proof-{recipe}-{compiler}"
+        logfile = OUT / f"{name}.log"
+        command = [
+            "taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--",
+            "timeout", "900s", str(binary), str(ROOT / "Standalone/data/owner_world.json"),
+            "--workers=12", "--world-assembler-prototype", "--stream-benchmark",
+            "--stream-pipeline", "--stream-hash", "--force-generate", "--clip-radius=3",
+            "--max-clip-level=8", "--max-level=-1",
+            f"--recipe={recipe}", "--audit-uniform-block-proofs", "--audit-route-parity",
+        ]
+        started = time.monotonic()
+        try:
+            with logfile.open("w", encoding="utf-8") as stream:
+                result = subprocess.run(command, cwd=ROOT, stdout=stream,
+                    stderr=subprocess.STDOUT, timeout=900, check=False)
+        except subprocess.TimeoutExpired:
+            result = None
+        elapsed = time.monotonic() - started
+        output = logfile.read_text(encoding="utf-8", errors="replace")
+        stamp = re.findall(
+            r"^\[WorldAssemblerRecipeAudit\] requested=([^ ]+) actual=([^ ]+).*status=([^ ]+)$",
+            output, re.M)
+        route = re.findall(r"^\[RouteParityAudit\].*$", output, re.M)
+        proofs = re.findall(r"^\[UniformBlockProofAudit\].*$", output, re.M)
+        stamp_ok = stamp == [(recipe, recipe, "PASS")]
+        route_ok = len(route) == 1 and route[0].endswith("status=PASS")
+        proof_ok = len(proofs) == 1 and bool(
+            re.search(r"violations=0(?:\s|$)", proofs[0]))
+        ok = (result is not None and result.returncode == 0 and stamp_ok
+              and route_ok and proof_ok)
+        code = result.returncode if result is not None else "TIMEOUT"
+        rows.append((name, recipe, compiler, elapsed, code, route_ok, bool(proof_ok), ok))
+        failed |= not ok
+        print(f"[L37LegacyAuditRun] case={name} elapsed={elapsed:.1f}s exit={code} "
+              f"recipe_stamp={'PASS' if stamp_ok else 'FAIL'} "
+              f"L13={'PASS' if route_ok else 'FAIL'} L9={'PASS' if proof_ok else 'FAIL'} "
+              f"{'PASS' if ok else 'FAIL'}", flush=True)
+
+summary = OUT / "legacy-audits.csv"
+summary.write_text(
+    "case,recipe,compiler,elapsed_seconds,exit_code,l13,l9,status\n" +
+    "".join(f"{name},{recipe},{compiler},{elapsed:.3f},{code},"
+        f"{'PASS' if l13 else 'FAIL'},{'PASS' if l9 else 'FAIL'},"
+        f"{'PASS' if ok else 'FAIL'}\n"
+        for name, recipe, compiler, elapsed, code, l13, l9, ok in rows),
+    encoding="utf-8")
+print(f"[L37LegacyAuditSummary] runs={len(rows)} pass={sum(row[-1] for row in rows)} "
+      f"fail={sum(not row[-1] for row in rows)} summary={summary}", flush=True)
+raise SystemExit(1 if failed or len(rows) != 4 else 0)