feat(view): ② coping card shows d_IP2 and the 계단 구간 표 (read-only, from the model)

The coping card lists d_IP2 and a table of the step segments: range, front and back coping tops, the lateral step, and
the block heights including the 50 mm pad (150 / 200 as in the 삽도). The table is read from the model; nothing new is
computed or entered. Tests check the P1 values against the 삽도.

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

tests/coping-steps.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it } from 'vitest';
+import { buildPier } from '../src/core/geometry';
+import { loadP1 } from './helpers';
+
+const m = buildPier(loadP1());
+const front = m.blocks.filter((b) => b.row === '전열');
+const back = m.blocks.filter((b) => b.row === '후열');
+
+describe('② 코핑 계단 구간 표 (2단계 읽기 전용, 시안 삽도)', () => {
+  it('P1 has five step segments from 0.000 to 12.000 m, as in the 삽도', () => {
+    expect(m.segments.length).toBe(5);
+    expect(m.segments[0].s0).toBeCloseTo(0, 6);
+    expect(m.segments[0].s1).toBeCloseTo(2.196, 3);
+    expect(m.segments[4].s1).toBeCloseTo(12, 6);
+  });
+
+  it('the front and back coping tops are 43.411 and 43.411 in the first segment, with no lateral step', () => {
+    expect(m.segments[0].top).toBeCloseTo(43.411, 3);
+    expect(back[0].bottom).toBeCloseTo(43.411, 3);
+    expect(Math.round((m.segments[0].top - back[0].bottom) * 1000)).toBe(0);
+  });
+
+  it('block heights including the 50 mm pad are 150 at the front and 200 at the back, as in the 삽도', () => {
+    expect(Math.round((front[0].padTop - front[0].bottom) * 1000)).toBe(150);
+    expect(Math.round((back[0].padTop - back[0].bottom) * 1000)).toBe(200);
+  });
+
+  it('d_IP2 is 1.134 m, as in the 삽도', () => {
+    expect(m.dIp2).toBeCloseTo(1.134, 3);
+  });
+});