wip: L175 fix tile seams - passage-affected X8 lanes use the composed path (v241, RED)

Seam audit: 0 mismatches over 16 seeds (99,269 pairs, 121.6M shared samples),
injected control detected. Step-2 overlap/turn failures remain. Mainline has the
same dispatch structure (not changed).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011g9Ez42ZNqQGjigc4FWDih

Standalone/Research/WorldAssemblerM3/Linux175/RunL175TimingAA.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+"""Measure same-binary timing spread for one L80 owner view and worker count."""
+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/l175/timing/aa-control"
+DATA = ROOT / "Standalone/data/owner_world.json"
+BINARY = ROOT / "Standalone/bin/linux/VoxelForgeCoreHeadless-l175-final-clang"
+CAMERA = "8.000000000000,16.000000000000,-372.262695312500,0,0"
+PIPELINE_RE = re.compile(r"^\[StreamPipeline\] (.*)$", re.M)
+FIELDS_RE = re.compile(r"([a-zA-Z0-9_]+)=([^ ]+)")
+NEAR_RE = re.compile(
+    r"^\[WorldAssemblerNearLODReady\] lods=0-2 tiles=(\d+)/(\d+) "
+    r"cold_ready_s=([0-9.]+)$", re.M)
+
+
+def run(label: str, phase: str, replicate: int) -> dict:
+    log = OUT / f"{label}-{phase}{replicate}.log"
+    command = [
+        "taskset", "-c", "0-11", "prlimit", "--as=6442450944", "--",
+        "timeout", "1740s", str(BINARY), str(DATA),
+        "--world-assembler-prototype", "--stream-benchmark", "--stream-pipeline",
+        "--seed=0", "--workers=8", "--clip-radius=3", "--max-clip-level=8",
+        "--max-level=8", f"--camera={CAMERA}", "--profile-lod-work",
+        "--stream-scheduler-policy=3",
+    ]
+    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")
+    pipeline, near = PIPELINE_RE.search(content), NEAR_RE.search(content)
+    if result.returncode or pipeline is None or near is None:
+        raise RuntimeError(f"A/A timing run failed: {log}; exit={result.returncode}")
+    fields = dict(FIELDS_RE.findall(pipeline.group(1)))
+    row = {
+        "label": label, "phase": phase, "replicate": replicate,
+        "lod02_ready_s": float(near.group(3)),
+        "whole_view_ready_s": float(fields["whole_view_ready"].removesuffix("s")),
+        "wall_s": round(time.monotonic() - started, 3),
+        "log": str(log.relative_to(ROOT)),
+    }
+    print("[L175TimingAA] " + json.dumps(row, sort_keys=True), flush=True)
+    return row
+
+
+def main() -> int:
+    if not DATA.is_file() or not BINARY.is_file():
+        raise SystemExit("missing owner input or final Clang binary")
+    OUT.mkdir(parents=True, exist_ok=True)
+    rows = [run("warmup", "warmup", 0)]
+    for replicate in range(1, 11):
+        rows.append(run("same-binary", "measured", replicate))
+        (OUT / "runs-partial.json").write_text(
+            json.dumps(rows, indent=2) + "\n", encoding="utf-8")
+    summary = {}
+    for key in ("lod02_ready_s", "whole_view_ready_s"):
+        values = [row[key] for row in rows if row["phase"] == "measured"]
+        summary[key] = {"values": values, "min": min(values), "max": max(values)}
+    (OUT / "summary.json").write_text(
+        json.dumps({"runs": rows, "summary": summary}, indent=2) + "\n",
+        encoding="utf-8")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())