feat(import): input template download with three sheets (spec 2.3 step 4)

- buildTemplateWorkbook: 교각 · IP · 받침 sheets with the headers the parser
  reads; value cells left empty so no blank-name rows raise E05
- dialog button 입력 템플릿 다운로드 (.xlsx)
- tests: sheet order, parser recognition, write-and-read round trip

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

index.html

@@ -117,6 +117,7 @@
               <input id="file" type="file" accept=".xlsx" hidden />
             </div>
             <p id="file-name" class="muted small"></p>
+            <button id="download-template" class="btn small" type="button">입력 템플릿 다운로드 (.xlsx)</button>
           </section>
 
           <section>

src/core/template.ts

@@ -0,0 +1,32 @@
+import * as XLSX from 'xlsx';
+
+/**
+ * Blank input template with the three sheets (교각 · IP · 받침) and the headers the parser looks for.
+ * Value cells are left empty on purpose: pre-filled names would become rows with no 교각명 and raise E05.
+ * Row 1–2 are notes; the parser finds the headers anywhere on the sheet.
+ */
+export function buildTemplateWorkbook(): XLSX.WorkBook {
+  const wb = XLSX.utils.book_new();
+  const note = (text: string) => [text];
+
+  const pier = [
+    note('교각 정보 1행당 교각 1기. 교각명·교각형식(T형/2주형/3주형)·기초 형식(말뚝기초/직접기초/현장타설말뚝)을 적습니다.'),
+    note('방위각은 75°56\'55.9" 형식으로 적습니다. 머리글 행은 바꾸지 마세요.'),
+    ['교각명', '교각형식', '두부보 EL_m', '기초 하단 EL_m', '지반고 EL_m', '기초 형식', '말뚝길이_mm', '두부보 폭_mm', '두부보 길이_mm', '기둥갯수'],
+  ];
+  const ip = [
+    note('IP1–IP4의 좌표(국토좌표계, m)와 코핑 꺾임각(°)을 적습니다. 교각명은 교각 정보와 같아야 합니다.'),
+    note('IP2는 참고용입니다. 프로그램이 IP1–IP3의 1:9 내분점으로 다시 계산해 비교합니다.'),
+    ['교각명', 'IP점', 'x_m', 'y_m', '코핑 꺾임각'],
+  ];
+  const bearing = [
+    note('받침 1행당 받침 1개. 전열·후열 수는 같아야 합니다. 위치는 전열 또는 후열.'),
+    note('z_m은 받침 EL(m), 방위각은 거더 방향입니다.'),
+    ['교각명', '받침번호', 'x_m', 'y_m', 'z_m', '방위각', '위치'],
+  ];
+
+  XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet(pier), '교각');
+  XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet(ip), 'IP');
+  XLSX.utils.book_append_sheet(wb, XLSX.utils.aoa_to_sheet(bearing), '받침');
+  return wb;
+}

src/main.ts

@@ -5,6 +5,7 @@ import * as XLSX from 'xlsx';
 import { parseWorkbook, type SheetReport } from './core/parseWorkbook';
 import { buildPier, type PierModel } from './core/geometry';
 import { NOT_IMPLEMENTED_RULES, validateInput, validatePier } from './core/validate';
+import { buildTemplateWorkbook } from './core/template';
 import type { Issue, PierInput, PierType } from './core/types';
 import { buildPierScene, viewPosition, type PartName, type PierScene, type ViewKind } from './view/scene';
 
@@ -520,6 +521,9 @@ $<HTMLButtonElement>('regen').addEventListener('click', regenerateChecked);
 $<HTMLInputElement>('project-name').addEventListener('input', updateApply);
 
 $<HTMLButtonElement>('pick-file').addEventListener('click', () => $<HTMLInputElement>('file').click());
+$<HTMLButtonElement>('download-template').addEventListener('click', () => {
+  XLSX.writeFile(buildTemplateWorkbook(), '교각입력템플릿.xlsx');
+});
 $<HTMLInputElement>('file').addEventListener('change', async (ev) => {
   const file = (ev.target as HTMLInputElement).files?.[0];
   if (!file) return;

tests/template.test.ts

@@ -0,0 +1,30 @@
+import * as XLSX from 'xlsx';
+import { describe, expect, it } from 'vitest';
+import { buildTemplateWorkbook } from '../src/core/template';
+import { parseWorkbook } from '../src/core/parseWorkbook';
+
+describe('input template (명세 §2.3 ④)', () => {
+  const wb = buildTemplateWorkbook();
+
+  it('has the three sheets 교각, IP, 받침 in that order', () => {
+    expect(wb.SheetNames).toEqual(['교각', 'IP', '받침']);
+  });
+
+  it('is recognised by the parser: each sheet has its table and no errors', () => {
+    const { piers, issues, sheets } = parseWorkbook(wb);
+    expect(piers).toEqual([]);
+    expect(issues).toEqual([]);
+    expect(sheets.map((s) => [s.name, s.tables])).toEqual([
+      ['교각', { pier: 1, ip: 0, bearing: 0 }],
+      ['IP', { pier: 0, ip: 1, bearing: 0 }],
+      ['받침', { pier: 0, ip: 0, bearing: 1 }],
+    ]);
+  });
+
+  it('round-trips through a file: written and re-read the same way', () => {
+    const bytes = XLSX.write(wb, { type: 'array', bookType: 'xlsx' }) as ArrayBuffer;
+    const back = XLSX.read(new Uint8Array(bytes), { type: 'array' });
+    expect(back.SheetNames).toEqual(['교각', 'IP', '받침']);
+    expect(parseWorkbook(back).issues).toEqual([]);
+  });
+});