feat(view): turn the bearing blocks, pads and block rebar to the bearing row (삽도)

Each block takes the skew of its bearing row against the perpendicular of its stretch axis (rowSkewDeg, from the bearing
azimuth). The blocks and pads are turned to that skew, and the S1/S2 bars are drawn in the block frame and turned with
it, so their lengths and embedments do not change. ② shows the row skew (P1: front −4.42°, back −3.11°). Approved
2026-10-23 with the drawing as reference.

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

tests/bearing-skew.test.ts

@@ -0,0 +1,44 @@
+import { describe, expect, it } from 'vitest';
+import { buildPier, blockFramePoint } from '../src/core/geometry';
+import { loadP1 } from './helpers';
+
+const model = buildPier(loadP1());
+const front = model.blocks.filter((b) => b.row === '전열');
+const back = model.blocks.filter((b) => b.row === '후열');
+
+describe('받침블럭 방위 (삽도 · 승인 2026-10-23)', () => {
+  it('P1 rows are skewed by the bearing azimuth against the axis perpendicular: front ≈ −4.42°, back ≈ −3.11°', () => {
+    expect(front.every((b) => Math.abs(b.rowSkewDeg - -4.42) < 0.02)).toBe(true);
+    expect(back.every((b) => Math.abs(b.rowSkewDeg - -3.11) < 0.02)).toBe(true);
+  });
+
+  it('a block side follows the bearing row: the n side of a block runs along (−sinδ, cosδ)', () => {
+    const b = front[0];
+    const [s1, n1] = blockFramePoint(b, 0, -0.6);
+    const [s2, n2] = blockFramePoint(b, 0, 0.6);
+    const ds = s2 - s1;
+    const dn = n2 - n1;
+    const len = Math.hypot(ds, dn);
+    const d = (b.rowSkewDeg * Math.PI) / 180;
+    expect(ds / len).toBeCloseTo(-Math.sin(d), 9);
+    expect(dn / len).toBeCloseTo(Math.cos(d), 9);
+  });
+
+  it('turning keeps the block centre and the bearing spacing (the row is unchanged)', () => {
+    const b = front[0];
+    const [s0, n0] = blockFramePoint(b, 0, 0);
+    expect(s0).toBeCloseTo(b.s, 12);
+    expect(n0).toBeCloseTo(b.n, 12);
+  });
+
+  it('the turned block corners stay inside the coping ends', () => {
+    const L = model.copingL;
+    for (const b of model.blocks) {
+      for (const [a, c] of [[-0.6, -0.6], [-0.6, 0.6], [0.6, -0.6], [0.6, 0.6]] as const) {
+        const [s] = blockFramePoint(b, a, c);
+        expect(s, `block ${b.no}`).toBeGreaterThan(0);
+        expect(s, `block ${b.no}`).toBeLessThan(L);
+      }
+    }
+  });
+});