feat(rebar): coping front view and 단면·폐합 section from the 3D bar records (승인 2026-10-26)

- rebar3d records every bar (name, stretch, local points, diameter) next to its
  mesh, so the 2D drawings use the same data as the 3D view.
- view/coping-rebar-svg.ts: the 정면 (along the coping length, EL vertical) and
  the 단면·폐합 at a chosen station (the bars crossing it, C9–C11 loops included).
- ③ coping tab: 정면 / 단면·폐합 toggle and the station input.

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

tests/coping-rebar-svg.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest';
+import { buildPier } from '../src/core/geometry';
+import { buildRebar3D } from '../src/view/rebar3d';
+import { copingBarGroup, copingFrontSvg, copingSectionSvg } from '../src/view/coping-rebar-svg';
+import { loadP1 } from './helpers';
+
+const model = buildPier(loadP1());
+const scene = buildRebar3D(model);
+
+describe('코핑 배근 정면 · 단면 (승인 2026-10-26)', () => {
+  it('the 3D bar records include the coping bars, the same data as the meshes', () => {
+    const coping = scene.records.filter((r) => /^C\d/.test(r.name));
+    expect(coping.length).toBeGreaterThan(0);
+    expect(scene.records.length).toBeGreaterThan(coping.length - 1);
+  });
+
+  it('the front view draws one polyline per coping bar', () => {
+    const coping = scene.records.filter((r) => /^C\d/.test(r.name));
+    const svg = copingFrontSvg(scene.records, model.copingL * 1000);
+    expect((svg.match(/<polyline/g) ?? []).length).toBe(coping.length);
+  });
+
+  it('groups the bars: C1–C8 main, C9–C11 loops, C12–C13 sides, C14–C16 steps', () => {
+    expect(copingBarGroup('C1')).toBe('main');
+    expect(copingBarGroup('C9')).toBe('loop');
+    expect(copingBarGroup('C12')).toBe('side');
+    expect(copingBarGroup('C15')).toBe('step');
+  });
+
+  it('the section at mid-length shows the bars that cross it', () => {
+    const svg = copingSectionSvg(scene.records, model.copingL / 2);
+    expect((svg.match(/<circle/g) ?? []).length).toBeGreaterThan(0);
+  });
+});