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/RunDeterminismL31.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+"""Re-run the L25 hash command and 24 m crossing on the L31 compiler matrix."""
+import re
+import subprocess
+import time
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[4]
+OUT = ROOT / "Saved/Linux/l31"
+OUT.mkdir(parents=True, exist_ok=True)
+BINARIES = {
+    "clang": OUT / "bin/VoxelForgeCoreHeadless-linux31-clang",
+    "gcc": OUT / "bin/VoxelForgeCoreHeadless-linux31-gcc",
+}
+HASH_PATTERN = re.compile(
+    r"^\[Pipeline(?:FullDetailHash|WholeViewHash|LODHash|ExactQueryHash)\].*$", re.M)
+rows = []
+failed = False
+candidate_reference = {}
+fi_hash_changes = {"l25": False, "crossing24": False}
+
+
+def hashes(path):
+    return HASH_PATTERN.findall(path.read_text(encoding="utf-8", errors="replace"))
+
+
+def run(kind, compiler, recipe, workers):
+    global failed
+    name = f"{kind}-{compiler}-{recipe}-w{workers}"
+    logfile = OUT / f"{name}.log"
+    command = [
+        str(BINARIES[compiler]), str(ROOT / "Standalone/data/owner_world.json"),
+        "--world-assembler-prototype", "--stream-benchmark", "--stream-pipeline",
+        "--stream-hash", "--force-generate", "--clip-radius=3", "--max-clip-level=8",
+        "--far-horizon-lod8-step=0", f"--workers={workers}", f"--recipe={recipe}",
+    ]
+    if kind == "crossing24":
+        command.extend(("--camera-step=24,0,0", "--region-crossing"))
+    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)
+    current = hashes(logfile)
+    # The normal L30 log stem is ringfix-hash; crossing uses ringfix-crossing24.
+    baseline = ROOT / "Saved/Linux/l30" / (
+        f"ringfix-crossing24-{compiler}-{recipe}-w{workers}.log" if kind == "crossing24"
+        else f"ringfix-hash-{compiler}-{recipe}-w{workers}.log")
+    reference = hashes(baseline) if baseline.is_file() else []
+    key = (kind, recipe)
+    prior = candidate_reference.get(key)
+    stable = prior is None or current == prior
+    if prior is None and current:
+        candidate_reference[key] = current
+    baseline_match = bool(reference) and current == reference
+    baseline_changed = bool(reference) and current != reference
+    if recipe == "surface-world":
+        baseline_ok = baseline_match
+        comparison = "MATCH" if baseline_match else "MISMATCH"
+    else:
+        baseline_ok = baseline_changed
+        comparison = "EXPECTED_CHANGE" if baseline_changed else "UNCHANGED_OR_MISSING"
+        fi_hash_changes[kind] |= baseline_changed
+    ok = (result is not None and result.returncode == 0
+          and stamps == [(recipe, recipe, "PASS")]
+          and "hash=on" in text and len(current) == 12 and stable and baseline_ok)
+    rows.append((kind, recipe, compiler, workers, elapsed,
+                 result.returncode if result else "TIMEOUT", len(current), ok))
+    print(f"{name} elapsed={elapsed:.1f}s recipe={stamps[0][1] if stamps else 'MISSING'} "
+          f"hashes={len(current)} "
+          f"L30={comparison} candidate_stable={'yes' if stable else 'no'} "
+          f"{'PASS' if ok else 'FAIL'}", flush=True)
+    if not ok:
+        failed = True
+
+
+for kind in ("l25", "crossing24"):
+    for recipe in ("surface-world", "floating-islands"):
+        for compiler in ("clang", "gcc"):
+            for workers in (1, 8, 12):
+                run("crossing24" if kind == "crossing24" else "l25", compiler, recipe, workers)
+
+summary = OUT / "determinism.csv"
+summary.write_text(
+    "kind,recipe,compiler,workers,elapsed_seconds,exit_code,hash_rows,status\n" +
+    "".join(f"{kind},{recipe},{compiler},{workers},{elapsed:.3f},{code},{count},"
+            f"{'PASS' if ok else 'FAIL'}\n"
+            for kind, recipe, compiler, workers, elapsed, code, count, ok in rows),
+    encoding="utf-8")
+for kind, changed in fi_hash_changes.items():
+    if not changed:
+        failed = True
+        print(f"[L31ExpectedGeometryHashChange] kind={kind} detected=false FAIL", flush=True)
+    else:
+        print(f"[L31ExpectedGeometryHashChange] kind={kind} detected=true PASS", flush=True)
+print(f"[L31Determinism] 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) != 24 else 0)