feat(rebar): C12 in the taper band (h2) and C13 in the end band (h1), from the coping geometry

The split between C12 and C13 follows the end underside, not a fixed level: C12 rows lie between the Level underside and
the end underside (taper height h2), C13 rows between the end underside and the top (end height h1). The break is the end
underside + 127 mm, the taper line's start at the end face. P1 is unchanged (C12 41.288–42.288, C13 42.538–42.788). Tests
check the band rule for h1 and h2 changes.

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

src/core/rebar/summary.ts

@@ -190,7 +190,7 @@ export function rebarSummary(
     warnings.push({ code: 'RB-M01', message: `다주형 ${nCol}기둥: C14는 T형 기준으로 두었습니다 (기둥마다 반복 규칙 미정, Q-K11).`, target: 'coping' });
   }
   // Per row: two 일자 (side faces) and two ㄷ (one at each end), so 4 bars per row (코핑철근.md §6.2).
-  const levels = sideRowLevels(model.levelBottom);
+  const levels = sideRowLevels(model.levelBottom, model.endBottom);
   const side = copingSideBars(model.copingL * 1000, levels.zBottom, levels.zBreak, model.copingGeom);
   const hook = model.copingB * 1000 - 2 * 127 + 2 * SIDE_HOOK_LEG; // ㄷ body across the width + two legs
   const c12Range = side.c12.length ? `${Math.round(side.c12[0].straight)}–${Math.round(side.c12[side.c12.length - 1].straight)}` : '—';