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>

tests/block-rebar-plan-svg.test.ts

@@ -0,0 +1,28 @@
+import { describe, expect, it } from 'vitest';
+import { buildPier } from '../src/core/geometry';
+import { blockRebarPlanSvg } from '../src/view/block-rebar-plan-svg';
+import { loadP1 } from './helpers';
+
+const count = (svg: string, re: RegExp) => (svg.match(re) ?? []).length;
+
+describe('받침블럭 배근 평면 (승인 2026-10-26)', () => {
+  it('a separate pair: 8 S2 and 8 S1 lines per block, each with two leg dots', () => {
+    const svg = blockRebarPlanSvg(buildPier(loadP1()), 0);
+    expect(count(svg, /stroke="#0F5C66" stroke-width="8"/g)).toBe(16);
+    expect(count(svg, /stroke="#B4531F" stroke-width="8"/g)).toBe(16);
+    expect(count(svg, /<circle/g)).toBe(64);
+  });
+
+  it('a 일체 pair: 19 S2 lines and 8 S1 lines, with their leg dots', () => {
+    const svg = blockRebarPlanSvg(buildPier({ ...loadP1(), bearingLayout: '일체' }), 0);
+    expect(count(svg, /stroke="#0F5C66" stroke-width="8"/g)).toBe(19);
+    expect(count(svg, /stroke="#B4531F" stroke-width="8"/g)).toBe(8);
+    expect(count(svg, /<circle/g)).toBe(54);
+  });
+
+  it('labels only the row numbers S1 and S2', () => {
+    const svg = blockRebarPlanSvg(buildPier(loadP1()), 0);
+    expect(svg).toContain('>S2<');
+    expect(svg).toContain('>S1<');
+  });
+});