feat(parse): join pier, IP, and bearing tables across sheets by 교각명

- one workbook may hold the three tables on separate sheets (user decision,
  recorded in DOC/03_설계); spec 2.2 one-sheet-per-pier is superseded
- E05 for rows whose 교각명 has no matching 교각 정보 row, or a pier missing IP/받침
- helper sheets (IP only, 받침 only) are shown as 보조 표 시트, not selectable
- test: three-sheet workbook built from the P1 sheet

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

src/main.ts

@@ -360,8 +360,10 @@ function renderDialog(): void {
   for (const sheet of p.sheets) {
     const li = el('li');
     const head = el('div', undefined);
+    const label =
+      sheet.piers === 0 ? (sheet.ok ? '보조 표 시트 (IP·받침)' : '오류') : sheet.ok ? '선택 가능' : '선택 불가 (오류)';
     head.append(
-      el('span', `${sheet.name} · ${sheet.ok ? '선택 가능' : '선택 불가 (오류)'}`, sheet.ok ? 'ok' : 'bad'),
+      el('span', `${sheet.name} · ${label}`, sheet.ok ? 'ok' : 'bad'),
       document.createTextNode(` · 교각 ${sheet.tables.pier}표 · IP ${sheet.tables.ip}표 · 받침 ${sheet.tables.bearing}표`),
     );
     li.appendChild(head);