feat(rebar): 단면·폐합 section shows only C1–C8 and C12·C13, with the top spacing labelled

- Other bars (C9–C11, C14–C16) are left out of the section; bubbles only for C1–6, C7·8, C12·13.
- The top-row chain carries the label 상면 간격.

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

tests/coping-rebar-svg.test.ts

@@ -36,10 +36,14 @@ describe('코핑 배근 정면 · 단면 (승인 2026-10-26)', () => {
 describe('단면 · 폐합 글자 겹침 (승인 2026-10-26)', () => {
   it('writes each bubble label once', () => {
     const svg = copingSectionSvg(scene.records, 6, model.copingRefTop, model.copingB * 1000);
-    // A bubble is drawn for each group that is cut at this station, and only once.
-    for (const label of ['C1–6', 'C12·13', 'C10', 'C7·8', 'C14', 'C16']) {
+    // Only the top row and the side rows are shown here: their bubbles, once each.
+    for (const label of ['C1–6', 'C7·8', 'C12·13']) {
       expect(svg.split(`>${label}<`).length - 1).toBe(1);
     }
+    for (const label of ['C10', 'C14', 'C16']) {
+      expect(svg).not.toContain(`>${label}<`);
+    }
+    expect(svg).toContain('상면 간격');
   });
 });