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/REPORT.md

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+# L141 — first liminal layer
+
+![flatField monolith, eye level](captures/flatField-monolith-eye.jpg)
+![periodicHills, eye level](captures/periodicHills-eye.jpg)
+![raised road, eye level](captures/raised-road-eye.jpg)
+
+![flatField monolith, wide](captures/flatField-monolith-wide.jpg)
+![periodicHills, wide](captures/periodicHills-wide.jpg)
+![raised road, wide](captures/raised-road-wide.jpg)
+
+The standalone fixtures and six captures are ready for review. The flat field has one oversized capped-cylinder monolith. The road is a 65 m `fillDais` platform, 6 m wide, with its deck 22 m above a flat field. Fog supplies the road's cloud-sea backdrop in these standalone images.
+
+The `periodicHills` fixture uses the validated 80 m periods and 2.2 m amplitudes on both axes. Its field repeats exactly, but these captures show one broad rise rather than hills repeating to the horizon. The validated period is longer than the 56 m eye-level capture radius; the wider full-detail capture exceeded Core's 160-million-node interval bound. Smaller periods fail the existing profile validator. A capture extent that trims vertical tiles independently from horizontal tiles is the next useful step; this round leaves the Core profile limits unchanged.
+
+## Changes
+
+- Reused Core's `flatField`, `periodicHills`, `fillMonolith`, and `fillDais` support. Added standalone fixture inputs and runners in `BuildL141Fixtures.py` and `CaptureL141.py`.
+- Added `liminal_road_override` as a standalone adapter to the existing free-placement `fillDais` stamp, plus `--audit-liminal-road-walk`. The walk audit samples the Core field with the existing capsule sampler and checks width and grade.
+- Added optional distance fog to `LinuxOffscreenCapture` for the screenshots. The fog is capture-only; Unreal cloud rendering remains Unreal-side.
+- No evaluator change or Unreal `Source/` change. Owner output hashes match their pinned L130/v227 canonical rows in the fast tier.
+
+## Measurements
+
+- Determinism: each fixture matched across Clang and GCC at W1, W8, and W12 (six cells per fixture). The matrix used LOD0, clip radius 1; each cell compares recipe/plan hashes, resolved-layout identity, and per-tile hashes. Individual logs are in `Saved/Linux/l141/logs/determinism-*.log`.
+- Raised-road capsule walk: 127 stations, 8,001 capsule samples, zero blocked samples, zero unsupported stations, 6.000 m width against a 0.680 m capsule diameter, and 0.000° grade. See `Saved/Linux/l141/logs/road-walk-audit.log`.
+- Near-ready: one W12 LOD0–2 sample after one warm-up, clip radius 1, 139/139 tiles. The measured `cold_ready_s` was **0.173886 s**. The window was one run after one warm-up; `uptime` showed a 1-minute load average of 1.31 and no other build was running. See `Saved/Linux/l141/logs/near-ready-measured.log`.
+- Each capture is 1600×900 and passed `capture_quality.py`. Eye views place the camera 1.6 m above the field or road deck. Camera coordinates and image hashes are recorded in the capture runner output; export and render logs are under `Saved/Linux/l141/logs/`.
+
+## Checks
+
+- Clang 19 and GCC standalone builds passed with FP contraction off, four jobs, and source stamp `0a2828c398aa62870690667901d44f2daf5b1a5547b9640da6dbb01df721af8b`.
+- `python3 Standalone/Tools/verify/verify.py fast --out Saved/Linux/l141 --overall-timeout 1740` passed in 285.7 s. Owner SurfaceWorld and FloatingIslands W1/W12 canonical hashes matched the L130/v227 baselines.
+- Fixture determinism, dedicated road walk audit, six standalone captures, and all six image-quality checks passed.
+- Python bytecode compilation and `git diff --check` passed.
+- An exploratory broad `--audit-resolved-layout-passages` invocation also ran unrelated passage ripple checks and reported 2/3 passage ripple records passing, with `passage/1-2/0` failing. The focused liminal road audit passes; no legacy threshold was changed.
+- No Unreal build was run because no Unreal `Source/` file changed. No timing matrix was requested or run.
+
+## Remaining risk
+
+The hill screenshots do not yet show multiple full repeats to the horizon. The profile itself is exactly periodic; the standalone capture volume is too short at the current full-detail safety bound. The raised road is geometric and walk-audited, while its clouds are represented by fog in the capture renderer.