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>

src/main.ts

@@ -24,6 +24,7 @@ import { bearingSectionSvg, type BearingDrawingRef } from './view/bearing-sectio
 import { solplateDetailSvg, type SolplateDrawingRef } from './view/solplate-svg';
 import { blockRebarSectionSvg } from './view/block-rebar-svg';
 import { blockRebarPlanSvg } from './view/block-rebar-plan-svg';
+import { copingFrontSvg, copingSectionSvg } from './view/coping-rebar-svg';
 import { BLOCK_REBAR_RANGES } from './core/rebar/block-check';
 import { DEFAULT_BLOCK_REBAR, type BlockRebarSettings } from './core/rebar/bearing-block';
 import { groundSectionSvg } from './view/ground-svg';
@@ -1069,6 +1070,50 @@ function renderBlockRebarSettings(box: HTMLDivElement, pier: Pier): void {
   box.appendChild(wrap);
 }
 
+/** 코핑 배근 (승인 2026-10-26, 추천): 정면, and the 단면·폐합 at a station the user chooses (default mid-length). */
+let copingView: 'front' | 'section' = 'front';
+let copingStation: number | null = null;
+
+function renderCopingDrawings(box: HTMLDivElement, pier: Pier): void {
+  if (!pier.model || !rebar3d) return;
+  const L = pier.model.copingL;
+  const wrap = el('div', undefined, 'bearing-ref');
+  const row = el('div', undefined, 'opts');
+  for (const [v, label] of [['front', '정면'], ['section', '단면 · 폐합 구성']] as const) {
+    const b = el('button', label, 'btn small');
+    b.type = 'button';
+    b.setAttribute('aria-pressed', String(copingView === v));
+    b.addEventListener('click', () => {
+      copingView = v;
+      renderAll();
+    });
+    row.appendChild(b);
+  }
+  wrap.appendChild(row);
+  const fig = el('figure', undefined, 'ground-fig');
+  if (copingView === 'front') {
+    fig.innerHTML = copingFrontSvg(rebar3d.records, L * 1000);
+    fig.appendChild(el('figcaption', '정면 · 교축 방향에서 본 코핑 배근 (3D 철근과 같은 데이터)', 'muted small'));
+  } else {
+    const at = copingStation ?? L / 2;
+    const station = el('input');
+    station.type = 'number';
+    station.step = '0.1';
+    station.value = String(at);
+    station.addEventListener('change', () => {
+      copingStation = Number(station.value);
+      renderAll();
+    });
+    const label = el('label', '단면 위치 s (m, 코핑 시작에서) ');
+    label.appendChild(station);
+    wrap.appendChild(label);
+    fig.innerHTML = copingSectionSvg(rebar3d.records, at);
+    fig.appendChild(el('figcaption', `단면 · 폐합 구성 · s = ${at} m에서 자른 철근 (C9–C11 폐합 포함)`, 'muted small'));
+  }
+  wrap.appendChild(fig);
+  box.appendChild(wrap);
+}
+
 function renderRebar(): void {
   const pier = activePier();
   // 교각 목록 with the 배근 status (시안 ③). The checks are the same as in ① and ②.
@@ -1103,6 +1148,7 @@ function renderRebar(): void {
   const { rows, warnings } = rebarSummary(pier.model, state.material, state.fckByMember);
   $('rebar-note').textContent = `${pier.input.name} · 형상 기준 계산 · 값은 기본값 기준 문서 규칙`;
   if (state.rebarMember === 'bearing') renderBlockRebarSettings(box, pier);
+  if (state.rebarMember === 'coping' && rebar3d) renderCopingDrawings(box, pier);
   const shown = rows.filter((r) => r.member === state.rebarMember);
   box.appendChild(rebarSelectBar(shown.map((r) => r.name)));
   const table = el('table', undefined, 'grid-table rebar-table');