proto: first liminal fixtures - flat field + monolith, periodic hills, raised road in fog (L141)

Standalone only: fixtures, liminal_road_override (fillDais), --audit-liminal-road-walk, capture-only distance fog.
Road 65 m x 6 m, 22 m up, capsule walk 127/127. Owner hashes unchanged (v227), fast tier, Clang/GCC green.
Hills repeat every 80 m but the capture reaches 56 m, so only one rise shows. Also R48 (who owns the tunnel mouth):
recommends a bounded joint plan of passage ports and layer landing candidates.

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

Standalone/Research/WorldAssemblerM3/Linux141/BuildL141Fixtures.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+"""Build three standalone liminal SurfaceWorld fixtures from the owner input."""
+from __future__ import annotations
+
+import argparse
+import json
+import os
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[4]
+OWNER = Path(os.environ.get("VOXELFORGE_OWNER_DATA",
+                            ROOT / "Standalone/data/owner_world.json"))
+OUT_DEFAULT = Path(os.environ.get("VOXELFORGE_VERIFY_OUT", ROOT / "Saved/Linux/l141"))
+
+FLAT_FIELD = {
+    "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"))
+
+    flat = dict(base)
+    flat["surface_profile_override"] = dict(FLAT_FIELD)
+    flat["motif_family_override"] = {
+        "version": 1,
+        "strate_index": 0,
+        "placement_policy": "seed,strate,stable_id",
+        "motifs": [
+            {
+                "stable_id": "liminal/oversized-familiar-monolith-v1",
+                "kind": "cappedCylinder",
+                "radius_m": 1.6,
+                "height_m": 26.0,
+                "route_side_offset_m": 42.0,
+                "placement_radius_m": 0.0,
+                "fillet_radius_m": 0.6,
+                "blend_width_m": 1.2,
+                "minimum_spacing_m": 0.0,
+                "yaw_quarter_turns": 0,
+                "attachment": "seated_floor",
+            },
+        ],
+    }
+
+    hills = dict(base)
+    hills["surface_profile_override"] = {
+        "version": 1,
+        "kind": "periodicHills",
+        "amplitude_x_m": 2.2,
+        "amplitude_y_m": 2.2,
+        "wavelength_x_m": 80.0,
+        "wavelength_y_m": 80.0,
+        "minimum_arena_clearance_m": 0.0,
+    }
+
+    road = dict(base)
+    road["surface_profile_override"] = dict(FLAT_FIELD)
+    road["liminal_road_override"] = {
+        "stable_id": "liminal/raised-road-v1",
+        "strate_index": 0,
+        "position_xy_m": [240.0, 180.0],
+        "half_extents_m": [32.5, 3.0, 0.75],
+        "deck_height_above_field_m": 22.0,
+        "yaw_quarter_turns": 0,
+    }
+
+    for name, fixture in (("flatField-monolith", flat),
+                          ("periodicHills", hills),
+                          ("raised-road", road)):
+        path = args.out / f"liminal-{name}.json"
+        path.write_text(json.dumps(fixture, indent=2) + "\n", encoding="utf-8")
+        print(f"[L141Fixture] name={name} file={path} status=PASS")
+
+
+if __name__ == "__main__":
+    main()