feat(view): 전단철근 구간 표 on the ③ coping tab (시안 ③)

- Segments of C9 (좌 경사), C10 (Level), C11 (우 경사): first and last bar in
  metres, spacing, count, and bar number. From the bar positions (코핑철근.md §3).
- Test: 0.300–4.550 (18 @250), 4.800–7.200 (9 @300), 7.450–11.700 (18 @250).
- Not verified in a browser.

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

tests/rebar-coping-lengths.test.ts

@@ -36,3 +36,14 @@ describe('삿갓과 조각 수 (코핑철근.md §4.3, Q-K5 추천안)', () => {
     expect(pieces).toBe(270);
   });
 });
+
+import { shearSegments } from '../src/core/rebar/coping';
+
+describe('전단철근 구간 표 (시안 ③)', () => {
+  it('left slope C9 0.300–4.550 (18, @250), Level C10 4.800–7.200 (9, @300), right slope C11 7.450–11.700 (18, @250)', () => {
+    const [left, level, right] = shearSegments(12000);
+    expect([left.from, left.to, left.count, left.spacing]).toEqual([300, 4550, 18, 250]);
+    expect([level.from, level.to, level.count, level.spacing]).toEqual([4800, 7200, 9, 300]);
+    expect([right.from, right.to, right.count, right.spacing]).toEqual([7450, 11700, 18, 250]);
+  });
+});