feat(abut-rebar): ③ 교대 흉벽 · 브라켓 3D 철근 (P1–P11)

- 흉벽 배근 경로를 교대 3D 철근에 추가 (저판 · 벽체와 같은 장면, 선택 · 색 기준 공통)
- 테스트: 철근표 = 3D 개수, 모든 흉벽 철근이 브라켓 배면 ~ 흉벽 전면, 흉벽 상단 아래 (P10은 슬래브로 300)

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

src/main.ts

@@ -687,13 +687,14 @@ function setupScene(): void {
     state.scene = scene;
     setView(state.view);
   }
-  // ③ 교대 (2026-11-04): with the piers hidden, the selected abutment's 저판 · 벽체 rebar is the ③ rebar (표 · 3D 선택 공통).
+  // ③ 교대 (2026-11-04): with the piers hidden, the selected abutment's 저판 · 벽체 · 흉벽 rebar is the ③ rebar (표 · 3D 선택 공통).
   const abutRec = piersShown(state.stage, state.abutActive) ? undefined : state.abutments.find((a) => a.name === state.abutActive);
   const abutGroup = abutRec ? abutGroupByName.get(abutRec.name) : undefined;
   const footing = abutRec ? abutFootingBuilt(abutRec) : null;
   if (abutRec && abutGroup && footing && footing.bottomEl !== undefined) {
     const wall = abutWallBuilt(abutRec, footing.result);
-    rebar3d = buildAbutRebar3D(footing.geom, footing.result, footing.skewK, footing.backM, footing.bottomEl, wall?.result);
+    const para = wall ? abutParapetBuilt(abutRec, wall) : null;
+    rebar3d = buildAbutRebar3D(footing.geom, footing.result, footing.skewK, footing.backM, footing.bottomEl, wall?.result, para?.result);
     rebar3d.group.applyMatrix4(abutGroup.matrix);
     rebar3d.group.visible = state.stage === 'rebar';
     rebar3d.setColorMode(state.rebarColor);