wip(assembler): round L31 -- FI recipe column audit corrected; recipe-stamped audit runner

On the real FloatingIslands recipe, column caps sit inside anchor-island rock and native bedrock;
the old check sampled the route foot. The audit now samples each planned cap against the native
field (negative control: a cap moved into air is detected). The audit runner records requested vs
actual recipe and exits on mismatch. All 16 passage rows (4 styles x 2 recipes x 2 compilers) pass.
The readable shader uses a smooth tint. Interim: FI Gradient displacement capped at width/256
(flat floor, no contour rings); restoring real undulation is L32. Evaluator 19.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

Standalone/Research/WorldAssemblerM3/Linux31/RunInvariantAuditsL31.py

@@ -0,0 +1,81 @@
+#!/usr/bin/env python3
+"""Run L31 route/proof and transition invariants with recipe-stamped logs."""
+import re
+import subprocess
+import time
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[4]
+OUT = ROOT / "Saved/Linux/l31"
+BINARIES = {
+    "clang": OUT / "bin/VoxelForgeCoreHeadless-linux31-clang",
+    "gcc": OUT / "bin/VoxelForgeCoreHeadless-linux31-gcc",
+}
+rows = []
+failed = False
+
+
+def run(name, binary, data, recipe, extra, checks):
+    global failed
+    logfile = OUT / f"{name}.log"
+    command = [
+        str(binary), str(data), "--workers=12", "--world-assembler-prototype",
+        "--stream-benchmark", "--stream-pipeline", "--force-generate",
+        "--clip-radius=3", "--max-clip-level=8", "--max-level=-1",
+        f"--recipe={recipe}", *extra,
+    ]
+    started = time.monotonic()
+    try:
+        with logfile.open("w", encoding="utf-8") as stream:
+            result = subprocess.run(command, stdout=stream, stderr=subprocess.STDOUT,
+                                    timeout=1800, check=False)
+    except subprocess.TimeoutExpired:
+        result = None
+    elapsed = time.monotonic() - started
+    text = logfile.read_text(encoding="utf-8", errors="replace")
+    stamps = re.findall(
+        r"^\[WorldAssemblerRecipeAudit\] requested=([^ ]+) actual=([^ ]+).*status=([^ ]+)$",
+        text, re.M)
+    stamp_ok = stamps == [(recipe, recipe, "PASS")]
+    checks_ok = all(check(text) for check in checks)
+    ok = result is not None and result.returncode == 0 and stamp_ok and checks_ok
+    rows.append((name, recipe, elapsed, result.returncode if result else "TIMEOUT", ok))
+    print(f"{name} elapsed={elapsed:.1f}s recipe={stamps[0][1] if stamps else 'MISSING'} "
+          f"stamp={'PASS' if stamp_ok else 'FAIL'} checks={'PASS' if checks_ok else 'FAIL'} "
+          f"{'PASS' if ok else 'FAIL'}", flush=True)
+    failed |= not ok
+
+
+owner = ROOT / "Standalone/data/owner_world.json"
+for recipe in ("surface-world", "floating-islands"):
+    for compiler, binary in BINARIES.items():
+        name = f"invariant-route-proof-{recipe}-{compiler}"
+        run(name, binary, owner, recipe,
+            ["--stream-hash", "--audit-uniform-block-proofs", "--audit-route-parity"],
+            [lambda text: bool(re.search(
+                 r"^\[RouteParityAudit\].*status=PASS$", text, re.M)),
+             lambda text: bool(re.search(
+                 r"^\[UniformBlockProofAudit\].*violations=0(?:\s|$)", text, re.M))])
+
+for recipe in ("surface-world", "floating-islands"):
+    for compiler, binary in BINARIES.items():
+        for mode in ("hard", "gradient", "interleaved"):
+            name = f"invariant-transition-{recipe}-{mode}-{compiler}"
+            run(name, binary, owner, recipe,
+                [f"--transition-mode={mode}", "--audit-strate-transitions"],
+                [lambda text: bool(re.search(
+                     r"^\[StrateTransitionAuditSummary\].*hole_columns=0 air_samples=0 .*status=PASS$",
+                     text, re.M)),
+                 lambda text: bool(re.search(
+                     r"^\[StrateTransitionNegativeControls\].*status=PASS$", text, re.M))])
+
+summary = OUT / "invariant-audits.csv"
+summary.write_text(
+    "run,recipe,elapsed_seconds,exit_code,status\n" +
+    "".join(f"{name},{recipe},{elapsed:.3f},{code},{'PASS' if ok else 'FAIL'}\n"
+            for name, recipe, elapsed, code, ok in rows),
+    encoding="utf-8")
+print(f"[L31InvariantAudits] 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) != 16 else 0)