feat(rebar): plan view of the block rebar with the 단면/평면 switch (승인 2026-10-26)

- view/block-rebar-plan-svg.ts: the selected pair from above — S2 lines along the
  교각축 (spaced at S2 across the 교축), S1 lines along the 교축 (spaced at S1),
  each end a dot (leg); the bar sets carry the row numbers only (S1, S2).
- The ③ card switches between the C–C section and the plan.

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

src/main.ts

@@ -23,6 +23,7 @@ import { bearingPlanSvg, type BearingPlanOverlay, PAIR_CHIP_LABELS } from './vie
 import { bearingSectionSvg, type BearingDrawingRef } from './view/bearing-section-svg';
 import { solplateDetailSvg, type SolplateDrawingRef } from './view/solplate-svg';
 import { blockRebarSectionSvg } from './view/block-rebar-svg';
+import { blockRebarPlanSvg } from './view/block-rebar-plan-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';
@@ -1048,8 +1049,22 @@ function renderBlockRebarSettings(box: HTMLDivElement, pier: Pier): void {
   const n = pier.model.integratedBlocks.length;
   wrap.appendChild(el('p', `적용 블럭: ${n > 0 ? `일체 ${n}쌍` : `분리 ${pier.model.blocks.length}개`} (전체)`, 'muted small'));
   const fig = el('figure', undefined, 'ground-fig');
-  fig.innerHTML = blockRebarSectionSvg(pier.model, Math.min(bearingPairIndex, Math.max(0, pairEccentricities(pier.model.blocks).length - 1)));
-  fig.appendChild(el('figcaption', '단면 C–C · 교축 방향 · 선택한 쌍 · S2 점(상면), S1 선과 다리(⊓) · 치수 mm', 'muted small'));
+  const pairIdx = Math.min(bearingPairIndex, Math.max(0, pairEccentricities(pier.model.blocks).length - 1));
+  // 단면 C–C / 평면 (승인 2026-10-26): the two views of the same settings; the 평면 shows the legs as dots and the row numbers.
+  const viewRow = el('div', undefined, 'opts');
+  for (const [v, label] of [['section', '단면 C–C'], ['plan', '평면']] as const) {
+    const b = el('button', label, 'btn small');
+    b.type = 'button';
+    b.setAttribute('aria-pressed', String(bearingRebarView === v));
+    b.addEventListener('click', () => {
+      bearingRebarView = v;
+      renderAll();
+    });
+    viewRow.appendChild(b);
+  }
+  wrap.appendChild(viewRow);
+  fig.innerHTML = bearingRebarView === 'plan' ? blockRebarPlanSvg(pier.model, pairIdx) : blockRebarSectionSvg(pier.model, pairIdx);
+  fig.appendChild(el('figcaption', bearingRebarView === 'plan' ? '평면 · 선택한 쌍 · S2 선(교각축 방향), S1 선(교축 방향) · 다리는 점 · 번호는 표의 행 번호' : '단면 C–C · 교축 방향 · 선택한 쌍 · S2 점(상면), S1 선과 다리(⊓) · 치수 mm', 'muted small'));
   wrap.appendChild(fig);
   box.appendChild(wrap);
 }
@@ -1589,6 +1604,8 @@ function renderBearingBasis(wrap: HTMLDivElement, pier: Pier): void {
 /** 상세 보기 pair shown in the plan, and whether the drawing values are overlaid (screen state only, 승인 2026-10-26). */
 let bearingPairIndex = 0;
 let bearingOverlayOn = true;
+/** ③ 받침블럭 view: the C–C section or the plan (승인 2026-10-26). */
+let bearingRebarView: 'section' | 'plan' = 'section';
 
 /**
  * Drawing values of one bearing for the overlays (승인 2026-10-26): the imported drawing row where it has the value

src/view/block-rebar-plan-svg.ts

@@ -0,0 +1,76 @@
+import type { PierModel } from '../core/geometry';
+import { blockFramePoint } from '../core/geometry';
+import { barDepths, barsAcross, type BlockRebarSettings } from '../core/rebar/bearing-block';
+import { pairEccentricities } from '../core/bearing-layout';
+import { INTEGRATED_BLOCK } from '../core/integrated-block';
+
+/**
+ * 받침블럭 배근 · 평면 (승인 2026-10-26): the blocks seen from above for the selected pair. x = 교축 (n), y = 교각축 (s).
+ * S2 bars run along the 교각축 (lines spaced across the 교축 at S2), S1 bars run along the 교축 (spaced along the 교각축 at S1).
+ * Each bar's ends are dots (the legs). The bar sets carry the table row numbers only (S1, S2).
+ */
+export function blockRebarPlanSvg(m: PierModel, pairIndex = 0): string {
+  const s: BlockRebarSettings = m.blockRebar;
+  const depth = barDepths(s);
+  const pair = pairEccentricities(m.blocks)[pairIndex];
+  if (!pair) return '';
+  const f = m.blocks.find((b) => b.no === pair.frontNo && b.row === '전열')!;
+  const k = m.blocks.find((b) => b.no === pair.backNo && b.row === '후열')!;
+  const ib = m.integratedBlocks.find((x) => x.frontNo === pair.frontNo);
+  const sc = ib ? ib.s : (f.s + k.s) / 2;
+  const nc = ib ? ib.n : (f.n + k.n) / 2;
+  const X = (n: number) => (n - nc) * 1000;
+  const Y = (sv: number) => (sv - sc) * 1000;
+  const parts: string[] = [];
+
+  // One block: a = along the 교각축 (s), c = along the 교축 (n), both in metres from the block centre, turned by the row skew.
+  const drawBlock = (cs: number, cn: number, skew: number, wA: number, wC: number) => {
+    const P = (a: number, c: number): [number, number] => {
+      const [sv, nv] = blockFramePoint({ s: cs, n: cn, rowSkewDeg: skew }, a, c);
+      return [X(nv), Y(sv)];
+    };
+    // Outline
+    const corners = [P(-wA / 2, -wC / 2), P(wA / 2, -wC / 2), P(wA / 2, wC / 2), P(-wA / 2, wC / 2)];
+    parts.push(`<polygon points="${corners.map((p) => p.join(',')).join(' ')}" fill="none" stroke="#6E8496" stroke-width="10"></polygon>`);
+    // S2: lines along the 교각축 at offsets across the 교축.
+    {
+      const a2s = barsAcross(wC * 1000, s.spacingS2, s);
+      const half = (wA * 1000 - 2 * s.coverSide) / 2000;
+      for (let i = 0; i < a2s.count; i++) {
+        const c = (a2s.firstEnd + i * a2s.spacing) / 1000 - wC / 2;
+        const p1 = P(-half, c);
+        const p2 = P(half, c);
+        parts.push(`<line x1="${p1[0]}" y1="${p1[1]}" x2="${p2[0]}" y2="${p2[1]}" stroke="#0F5C66" stroke-width="8"></line>`);
+        parts.push(`<circle cx="${p1[0]}" cy="${p1[1]}" r="14" fill="#0F5C66"></circle><circle cx="${p2[0]}" cy="${p2[1]}" r="14" fill="#0F5C66"></circle>`);
+      }
+    }
+    // S1: lines along the 교축 at offsets along the 교각축.
+    {
+      const a1s = barsAcross(wA * 1000, s.spacingS1, s);
+      const half = (wC * 1000 - 2 * s.coverSide) / 2000;
+      for (let i = 0; i < a1s.count; i++) {
+        const a = (a1s.firstEnd + i * a1s.spacing) / 1000 - wA / 2;
+        const p1 = P(a, -half);
+        const p2 = P(a, half);
+        parts.push(`<line x1="${p1[0]}" y1="${p1[1]}" x2="${p2[0]}" y2="${p2[1]}" stroke="#B4531F" stroke-width="8"></line>`);
+        parts.push(`<circle cx="${p1[0]}" cy="${p1[1]}" r="14" fill="#B4531F"></circle><circle cx="${p2[0]}" cy="${p2[1]}" r="14" fill="#B4531F"></circle>`);
+      }
+    }
+    return P;
+  };
+
+  if (ib) {
+    const P = drawBlock(ib.s, ib.n, ib.rowSkewDeg, INTEGRATED_BLOCK.depth / 1000, INTEGRATED_BLOCK.length / 1000);
+    // Row numbers: S2 and S1 once each, at the first bar's end.
+    const [sx, sy] = P(-0.6 + 0.1, -1.25 + 0.1);
+    parts.push(`<text x="${sx}" y="${sy - 40}" font-size="90" fill="#0F5C66">S2</text>`);
+    parts.push(`<text x="${sx + 200}" y="${sy + 150}" font-size="90" fill="#B4531F">S1</text>`);
+    parts.push(`<text x="0" y="${-800}" text-anchor="middle" font-size="90" fill="#18212B">${INTEGRATED_BLOCK.length}</text>`);
+  } else {
+    for (const b of [f, k]) drawBlock(b.s, b.n, b.rowSkewDeg, 1.2, 1.2);
+    const [sx, sy] = [X(f.n) - 500, Y(f.s) - 500];
+    parts.push(`<text x="${sx}" y="${sy}" font-size="90" fill="#0F5C66">S2</text>`);
+    parts.push(`<text x="${sx + 300}" y="${sy + 120}" font-size="90" fill="#B4531F">S1</text>`);
+  }
+  return `<svg viewBox="-1900 -1100 3800 2200" width="100%" style="max-width: 680px; height: auto" role="img" aria-label="받침블럭 배근 평면: S2 선과 S1 선, 다리는 점">${parts.join('')}</svg>`;
+}