feat(rebar): 상면 주철근(C1–C6) 이음 무시/반영, 위치 기둥 중심/단부

- 기본 '이음 무시' (사양 결정). '반영'이면 정척(12000) 초과 철근을 l_s 겹침 2조각으로 나눔
- 위치: 기둥 중심 = 전체의 절반, 단부 = 정척 안에서 가장 끝 쪽 (짧은 조각 = 전체 + l_s − 12000, 긴 조각 = 12000)
- 철근표 조각 목록과 비고, 3D 두 조각(l_s 겹침)에 반영
- STANDARD_BAR를 common.ts로 옮겨 순환 import 방지

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

src/core/rebar/summary.ts

@@ -1,12 +1,12 @@
 import type { PierModel } from '../geometry';
 import { barLength, bearingBlockRebar, DEFAULT_BLOCK_REBAR, totals } from './bearing-block';
 import { DEFAULT_COPING_REBAR } from './coping-settings';
-import { bottomPiece, topBarLength, widthLayout } from './coping-main';
+import { bottomPiece, topBarLength, widthLayout, topSplicePieces } from './coping-main';
 import { shearBars, shearBarsMulti, copingSideBars, SIDE_HOOK_LEG, c14Bars, c14Length, stairBars, stepDevLength, undersideAt, shearULength, capLength, PIECES_PER_POSITION } from './coping';
 import { sideRowLevels } from '../coping-geom';
 import { columnRebar, columnInputFor } from './column';
 import { bottomBars, crossBars, sideBars, assemblyBars, shearB9 } from './footing';
-import { DEFAULT_MATERIAL, FckByMember, fyOf, isAssumedMaterial, Material, materialFor, splitPieces } from './common';
+import { DEFAULT_MATERIAL, FckByMember, fyOf, isAssumedMaterial, Material, materialFor, splitPieces, STANDARD_BAR } from './common';
 
 /** 근거 badge (spec §6.1): where the value comes from. */
 export type Basis = 'input' | 'default' | 'calc' | 'assumed';
@@ -89,8 +89,7 @@ const FALLBACK: Pick<RebarRow, 'spacing' | 'actual' | 'position' | 'direction' |
   spacing: '—', actual: '—', position: '—', direction: '—', shape: '—', basis: 'calc',
 };
 
-/** 정척 L_bar (mm) from 확대기초철근.md §1.2. Bars longer than this need a splice. */
-export const STANDARD_BAR = 12000;
+export { STANDARD_BAR };
 
 /**
  * 철근표 for one pier (③ screen v1): bearing blocks, coping, column, footing. Built from the generated model.
@@ -195,8 +194,14 @@ export function rebarSummary(
     warnings.push({ code: 'CP04', message: `주철근 개수 ${width.count}(n+3)은 홀수라 cycle-1·cycle-2를 나눌 수 없습니다 (기본간격 ${width.spacing}, 끝단 여유 ${model.copingRebar.mainEndGap}). 기본간격을 확인하세요.`, target: 'coping' });
   }
   // C1–C3 and C4–C6 are the same three top rows (row 1, 2, 3), one set per cycle.
+  const AT_LABEL = { center: '기둥 중심', end: '단부' } as const;
   for (const [name, k] of [['C1', 1], ['C2', 2], ['C3', 3], ['C4', 1], ['C5', 2], ['C6', 3]] as const) {
-    rows.push({ member: 'coping', name, size: 'H29', count: perRow, length: topBarLength(L, k), note: '상면, 이음 무시' });
+    const sp = model.topSplice.mode === 'apply' ? topSplicePieces(L, k, model.topSplice.at, mCoping) : null;
+    if (sp) {
+      rows.push({ member: 'coping', name, size: 'H29', count: perRow, length: null, pieces: [{ length: sp.pieces[0], count: perRow }, { length: sp.pieces[1], count: perRow }], note: `상면, 2조각 겹침이음 (${AT_LABEL[model.topSplice.at]}, l_s ${Math.round(sp.lap)})` });
+    } else {
+      rows.push({ member: 'coping', name, size: 'H29', count: perRow, length: topBarLength(L, k), note: '상면, 이음 무시' });
+    }
   }
   const bottom = bottomPiece(mCoping);
   rows.push({ member: 'coping', name: 'C7', size: 'H29', count: perRow, length: bottom.piece, note: '하면, 2조각 겹침이음' });