feat(view): solplate taper across the 교각축 직각 (thick T1 at the (−) side); 교량받침 본체 as a box

The solplate's L (A + margin) runs across the 교각축 직각 and its W (B + margin) along the 교축; the top tapers across L with
T1 at the (−) side (T1 = T + L·|S|/200). The 교량받침 본체 is one box per bearing: the solplate plan less 100 mm on each
side, from the mortar top (EL.X) up h3 = 181 mm, turned with the bearing row. It is shown with the bearing group.

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

tests/solplate-scene.test.ts

@@ -31,4 +31,15 @@ describe('솔플레이트 모델과 3D (2단계, 승인 2026-10-23)', () => {
     const scene = buildPierScene(buildPier(loadP1()));
     expect(scene.parts.solplates.children.length).toBe(0);
   });
+
+  it('the 교량받침 본체 is one box per bearing: the solplate plan less 100 mm on each side, height h3 (181 mm)', () => {
+    const m = buildPier({ ...loadP1(), bearingPlans: plans, solplate: { T: 30, margin: 100, h3: 181 } });
+    const scene = buildPierScene(m);
+    const bodies = scene.parts.bearings.children;
+    expect(bodies.length).toBe(10);
+    const one = new THREE.Box3().setFromObject(bodies[0]);
+    expect(one.max.y - one.min.y).toBeCloseTo(0.181, 3);
+    // Body 1: L = 800 − 200 = 600 across the 교각축 직각, W = 740 − 200 = 540 along the 교축; the row skew turns it a few degrees.
+    expect(Math.max(one.max.x - one.min.x, one.max.z - one.min.z)).toBeGreaterThan(0.54);
+  });
 });