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>

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);
+  });
+});