feat(ground): load ground_model.json and apply the pier-centre ground EL

- ground-model.ts: read and check schema 1 of the Python ground model.
- ② 지반·지층 card: import the json, show the DTM value beside the excel
  value, and apply it only when the user presses the button (tracked as an
  override, revertible).
- groundEl becomes an editable, tracked input; the project file keeps the
  imported model and checks it on open.

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

src/core/changes.ts

@@ -19,6 +19,7 @@ export const EDITABLE_FIELDS = [
   { key: 'copingH2Mm', label: '테이퍼 높이 h2', unit: 'mm' },
   { key: 'levelWidthMm', label: 'Level 폭', unit: 'mm' },
   { key: 'pileLengthMm', label: '말뚝 길이', unit: 'mm' },
+  { key: 'groundEl', label: '지반고 EL', unit: 'm' },
 ] as const;
 
 /** Inputs tracked for overrides and pending changes: the numeric cards plus 열별 본수 (an array, compared by value). */
@@ -41,6 +42,7 @@ export const FIELD_LABELS: Record<EditableKey, string> = {
   copingH2Mm: '테이퍼 높이 h2',
   levelWidthMm: 'Level 폭',
   pileLengthMm: '말뚝 길이',
+  groundEl: '지반고 EL',
   pileRows: '열별 본수',
 };
 

src/core/ground-model.ts

@@ -0,0 +1,59 @@
+/**
+ * 지반 모델 결과 (RAG/pierzainer_ground의 ground_model.json, schema 1) 읽기.
+ * 앱은 교각 중심의 지반고만 쓴다. 적용은 사용자가 누를 때만 하며, 자동으로 입력을 바꾸지 않는다.
+ */
+
+/** Must match GROUND_MODEL_SCHEMA in the Python package. */
+export const GROUND_MODEL_SCHEMA = 1;
+
+export interface GroundModelPier {
+  /** 교각 이름 (입력의 name, 예: P1). */
+  id: string;
+  /** 지형 DTM으로 구한 교각 중심 지반고 (m). 자료 밖이면 null. */
+  centerEl: number | null;
+  /** 엑셀 지반고 (m). 없으면 null. */
+  excelEl: number | null;
+}
+
+export interface GroundModelFile {
+  schema: number;
+  generated: string;
+  piers: GroundModelPier[];
+}
+
+function numOrNull(v: unknown): number | null {
+  return typeof v === 'number' && Number.isFinite(v) ? v : null;
+}
+
+/** Checks the shape of a parsed ground_model.json. Throws with the first problem named in Korean. */
+export function checkGroundModel(raw: unknown): GroundModelFile {
+  const obj = raw as Partial<GroundModelFile> | null;
+  if (!obj || typeof obj !== 'object') throw new Error('지반 모델 파일 형식이 아닙니다.');
+  if (obj.schema !== GROUND_MODEL_SCHEMA) {
+    throw new Error(`지반 모델 형식 번호 ${String(obj.schema)}을(를) 읽을 수 없습니다 (지원: ${GROUND_MODEL_SCHEMA}).`);
+  }
+  if (!Array.isArray(obj.piers)) throw new Error('지반 모델 파일에 교각 목록(piers)이 없습니다.');
+  const piers = obj.piers.map((p, i) => {
+    const id = (p as { id?: unknown })?.id;
+    if (typeof id !== 'string' || !id) throw new Error(`지반 모델 ${i + 1}번째 교각의 이름(id)이 없습니다.`);
+    const ground = (p as { ground?: { center?: unknown; excel?: unknown } }).ground ?? {};
+    return { id, centerEl: numOrNull(ground.center), excelEl: numOrNull(ground.excel) };
+  });
+  return { schema: obj.schema, generated: typeof obj.generated === 'string' ? obj.generated : '', piers };
+}
+
+/** Parses the file text. Throws when it is not JSON or does not match the schema. */
+export function parseGroundModel(text: string): GroundModelFile {
+  let raw: unknown;
+  try {
+    raw = JSON.parse(text);
+  } catch {
+    throw new Error('지반 모델 파일이 JSON으로 읽히지 않습니다.');
+  }
+  return checkGroundModel(raw);
+}
+
+/** The DTM ground EL at the pier centre, or undefined when the model has no value for it. */
+export function groundElFor(model: GroundModelFile, pierName: string): number | undefined {
+  return model.piers.find((p) => p.id === pierName)?.centerEl ?? undefined;
+}

src/core/project.ts

@@ -1,4 +1,5 @@
 import type { FckByMember, Material } from './rebar/common';
+import { checkGroundModel, type GroundModelFile } from './ground-model';
 import type { PierInput } from './types';
 
 /** Project file schema (spec §8). Bump only with a migration. */
@@ -37,6 +38,8 @@ export interface ProjectFile {
   bearingDrawing?: Record<string, { no: number; elx: number; h1: number; h2: number }[]>;
   /** ② 부재별 fck (MPa). Absent in older files: every member uses the 공통 fck. */
   fckByMember?: FckByMember;
+  /** 지반 모델 (ground_model.json)의 교각별 지반고. Absent = 불러오지 않음. Applied to a pier only by the user. */
+  groundModel?: GroundModelFile;
 }
 
 /** Serialises a project to the pretty-printed JSON stored in <교량명>_교각설계.pzr.json. */
@@ -68,6 +71,7 @@ export function parseProject(text: string): ProjectFile {
       }
     }
   }
+  if (obj.groundModel !== undefined) checkGroundModel(obj.groundModel);
   obj.piers.forEach((p, i) => {
     if (!p || typeof p.id !== 'string' || !p.input) throw new Error(`교각 ${i + 1}: id 또는 input이 없습니다.`);
     const input = p.input;