fix(abut): 날개벽 헌치를 내측면 기준으로 재배치

- 뒷굽 헌치 삭제
- 연직 헌치 2개(흉벽 배면, 벽체 배면)를 날개벽 내측면 모서리에 평면 삼각형 기둥으로 둠
- 저판 상면 헌치 추가: 저판 상면과 날개벽 내측면 사이의 수평 헌치 (벽체 배면 → 뒷굽 구간, 다리 0.3 m)
- 테스트 갱신 (헌치 6개, 저판 상면 헌치 범위). 전체 639건 통과, 타입 검사·빌드 통과. 브라우저 시각 확인은 미실시

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

src/view/abut-scene.ts

@@ -8,7 +8,7 @@
 import * as THREE from 'three';
 import type { AbutModel, AbutPoint } from '../core/abut/geometry';
 import { buildMembers, type AbutMembers } from '../core/abut/members';
-import { buildWings, WING_THICKNESS_M, type WingSolid } from '../core/abut/wings';
+import { buildWings, HAUNCH_LEG_M, WING_THICKNESS_M, type WingSolid } from '../core/abut/wings';
 import type { TerrainGrid } from '../core/ground-model';
 import { terrainGeometry } from './terrain';
 
@@ -284,10 +284,14 @@ export function buildAbutGroup(
     const lower = prism(clipBelowX(below, members.shape.wallBackM / dir.wt), WING_THICKNESS_M, new THREE.Vector3(sEnd, 0, 0), ax, ey, new THREE.Vector3(a, 0, 0));
     add('wings', upper, 0xc9a77c);
     add('wings', lower, 0xc9a77c);
-    // 뒷굽 헌치 (삽도): (t, EL) triangle, extruded across the wing thickness along s.
-    if (wing.heelHaunch) {
-      const profile = wing.heelHaunch;
-      add('haunches', prism(profile, WING_THICKNESS_M, new THREE.Vector3(sEnd, 0, 0), ez, ey, new THREE.Vector3(a, 0, 0)), 0xc9a77c);
+    // 저판 상면 헌치 (수평, 2026-11-03): a right triangle in the plane EL–s on the 저판 상면, next to the 날개벽 내측면,
+    // extruded along the wing from the 벽체 배면 to the 뒷굽.
+    if (wing.footingHaunch) {
+      const f = wing.footingHaunch;
+      const leg = HAUNCH_LEG_M;
+      const triangle: [number, number][] = [[0, 0], [leg, 0], [0, leg]];
+      const origin = new THREE.Vector3(sEnd + a * WING_THICKNESS_M + dir.ws * f.dMFrom, f.el, dir.wt * f.dMFrom);
+      add('haunches', prism(triangle, f.dMTo - f.dMFrom, origin, new THREE.Vector3(a, 0, 0), ey, new THREE.Vector3(dir.ws, 0, dir.wt)), 0xc9a77c);
     }
     for (const h of wing.haunches) {
       const shape: [number, number][] = h.corners.map((c) => {