feat(ground): pile-tip embedment check and soil layers from the ground model

- ground.ts: G04 when a pile tip is above the 연암 상면 minus 1.0 × D; G05
  (info) when layers are entered but there is no 연암 row. No message while
  no layers are entered at all.
- ground-model.ts: reads the Python soil.layers as strata rows; the project
  file keeps and checks them.
- ② card: a button fills the layer rows from the ground model for the pier.

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

src/core/ground.ts

@@ -1,3 +1,4 @@
+import type { PierModel } from './geometry';
 import type { Issue, PierInput } from './types';
 
 /** 위치 choices of the 지반·지층 card (시안 2026-10-26). */
@@ -9,6 +10,9 @@ export const STRATA_NAMES = ['매립토', '퇴적토', '풍화토', '풍화암',
 /** The 지지층 for the pile tip check (지반 모델 G-7). */
 export const SUPPORT_STRATUM = '연암';
 
+/** 근입 = 이 값 × 말뚝 지름 (지반 모델 G-7, embed_d 1.0). */
+export const PILE_EMBED_D = 1.0;
+
 /**
  * 지반·지층 입력 검사 (승인 2026-10-26).
  * G01: 층 하단 EL은 위 경계보다 낮아야 함. G02: 지하수위는 지반고와 가장 아래 층 사이에 있어야 함.
@@ -37,3 +41,33 @@ export function validateGround(input: PierInput, issues: Issue[]): void {
     }
   }
 }
+
+/**
+ * 말뚝 선단 근입 (승인 2026-10-26): every pile tip must be at least PILE_EMBED_D × D below the 연암 상면.
+ * G04: a tip above that limit. G05 (info): piles but no 연암 row, so the embedment is not checked.
+ * The 연암 상면 is the bottom of the row above the 연암 row (ground EL for the first row).
+ */
+export function validatePileEmbedment(input: PierInput, model: PierModel, issues: Issue[]): void {
+  if (model.piles.length === 0) return;
+  const rows = input.strataRows ?? [];
+  const k = rows.findIndex((r) => r.name === SUPPORT_STRATUM);
+  if (k < 0) {
+    // No layers entered yet: nothing to say. Layers entered but no 연암 row: say so.
+    if (rows.length > 0) {
+      issues.push({ code: 'G05', level: 'I', pier: input.name, message: '연암 행이 없어 말뚝 선단 근입을 확인하지 않았습니다.' });
+    }
+    return;
+  }
+  const top = k === 0 ? input.groundEl : rows[k - 1].bottomEl;
+  const deepest = Math.max(...model.piles.map((p) => p.bottom));
+  const diameter = Math.max(...model.piles.map((p) => p.diameter));
+  const limit = top - PILE_EMBED_D * diameter;
+  if (deepest > limit + 1e-9) {
+    issues.push({
+      code: 'G04',
+      level: 'W',
+      pier: input.name,
+      message: `말뚝 선단 EL ${deepest.toFixed(3)}이 연암 상면 ${top.toFixed(3)} − 근입 ${(PILE_EMBED_D * diameter).toFixed(3)} = ${limit.toFixed(3)}보다 높습니다.`,
+    });
+  }
+}