feat(rebar): 단면·폐합 at two fixed stations side by side (단부 0.3 m, first column centre)

- The station input is removed. The section shows the 단부 (first shear
  station, from the 3D bar records) and the first column centre, side by side.
- The 상면 간격 label is removed.

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

src/main.ts

@@ -24,7 +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 { copingEndStation, 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';
@@ -1072,7 +1072,6 @@ function renderBlockRebarSettings(box: HTMLDivElement, pier: Pier): void {
 
 /** 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;
@@ -1095,20 +1094,19 @@ function renderCopingDrawings(box: HTMLDivElement, pier: Pier): void {
     fig.innerHTML = copingFrontSvg(rebar3d.records, L * 1000, pier.model.columns[0]?.s ?? 0);
     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, pier.model.copingRefTop, pier.model.copingB * 1000);
-    fig.appendChild(el('figcaption', `단면 · 폐합 구성 · s = ${at} m에서 자른 철근 (C9–C11 폐합 포함)`, 'muted small'));
+    // 단면 · 폐합 at two fixed stations side by side (승인 2026-10-26): the 단부 (first shear station) and the first column centre.
+    const sEnd = copingEndStation(rebar3d.records);
+    const sCol = pier.model.columns[0]?.s ?? L / 2;
+    const grid = el('div', undefined, 'footing-grid');
+    for (const [st, label] of [[sEnd, `단부 s = ${sEnd.toFixed(2)} m`], [sCol, `기둥 중심 s = ${sCol.toFixed(2)} m`]] as const) {
+      const f = el('figure', undefined, 'footing-fig');
+      f.innerHTML = copingSectionSvg(rebar3d.records, st, pier.model.copingRefTop, pier.model.copingB * 1000);
+      f.appendChild(el('figcaption', label, 'muted small'));
+      grid.appendChild(f);
+    }
+    wrap.appendChild(grid);
+    box.appendChild(wrap);
+    return;
   }
   wrap.appendChild(fig);
   box.appendChild(wrap);

src/view/coping-rebar-svg.ts

@@ -53,6 +53,12 @@ export function chainDims(positions: number[], startMm: number, endMm: number):
   return out;
 }
 
+/** The 단부 station (m): the first station of the 전단·띠 bars (C9–C11), i.e. the first shear position. */
+export function copingEndStation(records: BarRecord[]): number {
+  const loops = records.filter((r) => /^C(9|10|11)$/.test(r.name));
+  return Math.min(...loops.flatMap((r) => r.pts.map((p) => p[0])));
+}
+
 /**
  * Bar positions (mm, along the coping): one per bar, its mean s. A loop or a cross bar sits at one station, so its
  * points share the same s apart from the bends; the bends are not positions of their own.
@@ -221,7 +227,6 @@ export function copingSectionSvg(records: BarRecord[], s0: number, copingTopEl?:
   for (const d of topChain) {
     parts.push(`<line x1="${d.from}" y1="${dimTop}" x2="${d.to}" y2="${dimTop}" stroke="#18212B" stroke-width="8"></line><text x="${(d.from + d.to) / 2}" y="${dimTop - 90}" text-anchor="middle" font-size="160" fill="#18212B">${d.text}</text>`);
   }
-  parts.push(`<text x="${(-halfW + halfW) / 2}" y="${dimTop - 260}" text-anchor="middle" font-size="150" fill="#55606E">상면 간격</text>`);
 
   // 4: the side rows (C12·C13) along the EL, from the coping top EL down to the lowest side bar.
   const side = unique.filter((c) => c.group === 'side' && c.x < 0);

tests/coping-rebar-svg.test.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest';
 import { buildPier } from '../src/core/geometry';
 import { buildRebar3D } from '../src/view/rebar3d';
-import { chainDims, copingBarGroup, copingFrontSvg, copingSectionSvg } from '../src/view/coping-rebar-svg';
+import { chainDims, copingBarGroup, copingEndStation, copingFrontSvg, copingSectionSvg } from '../src/view/coping-rebar-svg';
 import { loadP1 } from './helpers';
 
 const model = buildPier(loadP1());
@@ -43,7 +43,7 @@ describe('단면 · 폐합 글자 겹침 (승인 2026-10-26)', () => {
     for (const label of ['C10', 'C14', 'C16']) {
       expect(svg).not.toContain(`>${label}<`);
     }
-    expect(svg).toContain('상면 간격');
+    expect(svg).not.toContain('상면 간격');
   });
 });
 
@@ -96,3 +96,9 @@ describe('아래 치수선의 0 = 기둥 중심 (승인 2026-10-26)', () => {
     expect((span![0] + span![1]) / 2).toBeCloseTo(col, 0);
   });
 });
+
+describe('단부 위치 (승인 2026-10-26)', () => {
+  it('the 단부 section is at the first shear station, 0.3 m from the coping start for P1', () => {
+    expect(copingEndStation(scene.records)).toBeCloseTo(0.3, 6);
+  });
+});