feat(core): profiled heightfields, slice 1: periodicHills, mirroredRelief, flatField (L53); research R22

WorldAssemblySurfaceProfileV1 on the native SurfaceWorld recipe and plan; version 0 'natural' is omitted
from serialized identity, so the owner world is unchanged. periodicHills (seeded cosine hills, plan-time
grade <= 15 deg), mirroredRelief (cap mirrors the floor by lambda, clearance checked) and flatField share
one profile function for points, lattice classification and exact cosine-extrema intervals (0 interval
misses in brute-force audits). Style-override fixtures with planned passages. Cold whole view about 1.33 s
for each profile vs 1.74 s natural SW (Clang). Owner hashes identical to L52; fast/medium/full PASS.
Research R22: SurfaceWorld critical path to about 1 s.

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

Standalone/Research/WorldAssemblerM3/Linux53/BuildProfileFixturesL53.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+"""Build the three named style-override inputs for the profiled heightfield slice."""
+import argparse
+import json
+import os
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[4]
+OWNER = ROOT / "Standalone/data/owner_world.json"
+OUT_DEFAULT = Path(os.environ.get("VOXELFORGE_VERIFY_OUT", ROOT / "Saved/Linux/l53"))
+PROFILES = {
+    "periodicHills": {
+        "version": 1,
+        "kind": "periodicHills",
+        "amplitude_x_m": 1.5,
+        "amplitude_y_m": 1.5,
+        "wavelength_x_m": 96.0,
+        "wavelength_y_m": 96.0,
+        "minimum_arena_clearance_m": 0.0,
+    },
+    "mirroredRelief": {
+        "version": 1,
+        "kind": "mirroredRelief",
+        "amplitude_x_m": 1.5,
+        "amplitude_y_m": 1.5,
+        "wavelength_x_m": 128.0,
+        "wavelength_y_m": 128.0,
+        "mirror_lambda": 0.875,
+        "minimum_arena_clearance_m": 8.0,
+    },
+    "flatField": {
+        "version": 1,
+        "kind": "flatField",
+        "minimum_arena_clearance_m": 0.0,
+    },
+}
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--out", type=Path, default=OUT_DEFAULT / "fixtures")
+    args = parser.parse_args()
+    args.out.mkdir(parents=True, exist_ok=True)
+    base = json.loads(OWNER.read_text(encoding="utf-8"))
+    for name, override in PROFILES.items():
+        fixture = dict(base)
+        fixture["surface_profile_override"] = override
+        path = args.out / f"style-override-profile-{name}.json"
+        path.write_text(json.dumps(fixture, indent=2) + "\n", encoding="utf-8")
+        print(f"[L53ProfileFixture] name={path.stem} profile={name} path={path} status=PASS")
+
+
+if __name__ == "__main__":
+    main()