Reapply "feat(rebar): B1–B4와 B5–B8 방향 교환 (B1–B4는 W 방향, B5–B8은 L 방향)"

사용자 요청으로 방향 교환을 다시 적용 (99db6a1 되돌림). 격자 키 sL/sW, 3D·단면·철근표 역할과 테스트 기대값이 교환 기준으로 돌아감.

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

tests/footing-section-svg.test.ts

@@ -17,16 +17,15 @@ describe('확대기초 교각축 직각 단면 (폭 W) (승인 2026-10-26, 추
   const svg = footingSectionSvg(m);
 
   it('point and line counts match the rebar table families', () => {
-    const bottom = bottomBars(L, W, H, fs);
-    expect(countMark(svg, 'b1', 'B1')).toBe(bottom.find((b) => b.name === 'B1')!.count);
-    expect(countMark(svg, 'b2', 'B2')).toBe(bottom.find((b) => b.name === 'B2')!.count);
-    expect(countMark(svg, 'b4', 'B4')).toBe(bottom.find((b) => b.name === 'B4')!.count);
+    const cross = crossBars(L, W, H, fs);
+    // B1–B4 run along W: one line per family in this section; B5–B8 run along L: points on the W grid (방향 교환).
+    for (const name of ['B1', 'B2', 'B3', 'B4']) expect(countMark(svg, name.toLowerCase(), name)).toBe(1);
+    for (const name of ['B5', 'B6', 'B7', 'B8']) expect(countMark(svg, name.toLowerCase(), name)).toBe(cross.find((b) => b.name === name)!.count);
     expect(countMark(svg, 'b9', 'B9')).toBe(b9Bars(L, W, [], 2000, fs).rows);
     expect(countMark(svg, 'b10', 'B10-1')).toBe(sideBars(L, W, H, fs).find((b) => b.name === 'B10-1')!.count);
     expect(countMark(svg, 'b11', 'B11')).toBe(assemblyJs(H, fs).length);
     expect(countMark(svg, 'b12', 'B12')).toBe(assemblyBars(L, W, H, fs).find((b) => b.name === 'B12')!.count);
-    for (const name of ['B5', 'B6', 'B7', 'B8']) expect(countMark(svg, 'b5', name)).toBe(1);
-    expect(crossBars(L, W, H, fs).length).toBe(4);
+    expect(cross.length).toBe(4);
   });
 
   it('shows the width, the grid string, and the B10 levels as dimensions', () => {