wip(assembler): round L18 -- FloatingIslands false floors removed; shared strate ceiling

FI geometry v3 drops the all-XY lower boundary seal that created false floors (3.5/8 m); the
ceiling comes from the shared VF_ApplyUpperBoundarySeal and AppendStratumBoundaryCeilings path
for every generator, at each strate's own configured upper boundary (owner: every strate has a
ceiling). Far-LOD ceiling continuity: 0 gaps at LOD4-8. SurfaceWorld bit-identical to L14
(14 configs + 24 m crossing); FI deterministic (28-row matrix); route parity and proofs pass.
Unreal: FI geometryVersion 2->3 and the shared upper-seal helper extracted (UBT compile needed on
the owner PC). Open: small ceiling holes; lower-stratum LOD ring steps seen through the FI void.

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

Standalone/Research/WorldAssemblerM3/Linux18/CaptureLinux18.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""Render the matched L18 review views as small readable JPEGs."""
+import os
+import subprocess
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[4]
+CAPTURE = ROOT / "Standalone/bin/linux/VoxelForgeOffscreenCapture-linux18-clang"
+EXPORTS = ROOT / "Standalone/Research/WorldAssemblerM3/Linux18/exports"
+OUT = ROOT / "Standalone/Research/WorldAssemblerM3/Linux18/captures"
+LOGS = ROOT / "Saved/Linux"
+OUT.mkdir(parents=True, exist_ok=True)
+env = os.environ.copy()
+env["LP_NUM_THREADS"] = "12"
+env["XDG_CACHE_HOME"] = str(ROOT / "Saved/Linux/mesa-cache")
+
+views = [
+    ("floating-islands-flat-square-after", "floating-islands-flat-square.vfmesh",
+     (-11.612444, -118.221237, -19.8452), 0, 0, True),
+    ("floating-islands-flat-square-no-edges", "floating-islands-flat-square.vfmesh",
+     (-11.612444, -118.221237, -19.8452), 0, 0, False),
+    ("floating-islands-island-view-after", "floating-islands-island-view.vfmesh",
+     (-22, -19, -22.8), 0, -4, True),
+    ("floating-islands-ceiling-up", "floating-islands-island-view.vfmesh",
+     (-22, -19, -22.8), 0, 80, True),
+    ("surface-world-l1-spawn-after", "surface-world-l1-spawn.vfmesh",
+     (0, -35, -487.94), 0, -22, False),
+    ("surface-world-horizon-after", "surface-world-l1-spawn.vfmesh",
+     (0, -35, -487.94), 0, 0, False),
+]
+
+for name, scene_name, camera, yaw, pitch, tile_edges in views:
+    scene = EXPORTS / scene_name
+    png = LOGS / f"l18-{name}.png"
+    jpg = OUT / f"{name}.jpg"
+    render_log = LOGS / f"l18-{name}-render.log"
+    convert_log = LOGS / f"l18-{name}-jpeg.log"
+    command = [str(CAPTURE), str(scene), str(png), "--size=1600x900",
+        "--shade=readable", f"--tile-edges={'on' if tile_edges else 'off'}",
+        "--tile-edge-width-m=0.15", "--camera-m="+",".join(map(str, camera)),
+        f"--yaw-deg={yaw}", f"--pitch-deg={pitch}"]
+    with render_log.open("w", encoding="utf-8") as stream:
+        subprocess.run(command, cwd=ROOT, env=env, stdout=stream,
+                       stderr=subprocess.STDOUT, check=True)
+    ffmpeg = ["ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "error", "-y",
+        "-i", str(png), "-frames:v", "1", "-q:v", "4", str(jpg)]
+    with convert_log.open("w", encoding="utf-8") as stream:
+        subprocess.run(ffmpeg, cwd=ROOT, env=env, stdout=stream,
+                       stderr=subprocess.STDOUT, check=True)
+    if jpg.stat().st_size > 300_000:
+        raise SystemExit(f"{jpg.name} exceeds the 300 KB review limit")
+    print(f"[Capture] {jpg.relative_to(ROOT)} bytes={jpg.stat().st_size} status=PASS")