feat(rebar): 현장타설 말뚝 · 다주형 코핑 형상과 철근 계산

- 현장타설 기둥·말뚝 형상(cast-in-place-shape)과 주철근·횡철근·커플러 계산(rebar/cast-in-place, cast-layout)
- 다주형 코핑 철근(multicol-coping), 기둥 높이 · 양단부 연장
- 철근표 요약 · 재료 수량 · 3D 뷰 연결과 삽도(cast-rebar-svg)
- 검사 기준 갱신과 회귀 테스트, 검증 스크립트 보관

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

src/core/cast-in-place-shape.ts

@@ -0,0 +1,51 @@
+import type { PierInput } from './types';
+
+/** EL in metres, lengths in mm. User image and clarifications, 2026-11-05. */
+export interface CastInPlaceShapeSettings {
+  betaLengthMm?: number;
+  weatheredRockEl?: number;
+  bedrockEl?: number;
+  casingOn?: boolean;
+  casingTopEl?: number;
+  casingBottomEl?: number;
+  clayBottomEl?: number;
+}
+
+export function castShape(input: Pick<PierInput, 'groundEl' | 'pileLengthMm' | 'castInPlaceShape'>) {
+  const s = input.castInPlaceShape ?? {};
+  const pileBottomEl = input.groundEl - input.pileLengthMm / 1000;
+  const bedrockEl = s.bedrockEl ?? pileBottomEl + 1;
+  const betaLengthMm = s.betaLengthMm ?? 9000;
+  return {
+    pileTopEl: input.groundEl, pileBottomEl,
+    betaLengthMm, betaEl: input.groundEl - betaLengthMm / 1000,
+    weatheredRockEl: s.weatheredRockEl ?? pileBottomEl + 5,
+    bedrockEl,
+    casingOn: s.casingOn ?? false,
+    casingTopEl: s.casingTopEl ?? input.groundEl + 3,
+    casingBottomEl: s.casingBottomEl ?? bedrockEl,
+    clayBottomEl: s.clayBottomEl,
+  };
+}
+
+export function castShapeIssues(value: unknown): string[] {
+  if (value === undefined) return [];
+  if (!value || typeof value !== 'object' || Array.isArray(value)) return ['현장타설 형상 입력 형식이 맞지 않습니다.'];
+  const out: string[] = [];
+  for (const [key, v] of Object.entries(value)) {
+    if (v === undefined) continue;
+    if (key === 'casingOn') { if (typeof v !== 'boolean') out.push('희생강관 적용 여부가 맞지 않습니다.'); }
+    else if (!['betaLengthMm', 'weatheredRockEl', 'bedrockEl', 'casingTopEl', 'casingBottomEl', 'clayBottomEl'].includes(key) || typeof v !== 'number' || !Number.isFinite(v) || key === 'betaLengthMm' && v <= 0) out.push(`현장타설 형상 ${key} 값이 맞지 않습니다.`);
+  }
+  return out;
+}
+
+/** DXF note 4. Do not substitute weathered-rock EL for the independent clay-layer EL. */
+export function castLowerZone(input: Pick<PierInput, 'groundEl' | 'pileLengthMm' | 'castInPlaceShape' | 'columnDiameterMm'>) {
+  const s = castShape(input);
+  if (s.clayBottomEl === undefined) return null;
+  const d = (input.columnDiameterMm ?? 2000) / 1000;
+  const a = s.betaEl - 3 * d;
+  const b = s.clayBottomEl + d;
+  return { bottomEl: a, topEl: b, valid: a < b };
+}