feat(rebar): piece lengths for C9–C13 and P1·P2 so the 재료표 has no missing bars

A row can now carry pieces (length, count). C9, C10, C11 and C9·C11 사이 have U and 삿갓 pieces per position (3 loops each);
C12 and C13 have 일자 and ㄷ pieces per bar; P1 and P2 have their splice pieces, each counting all the bars. The
재료표 totals from the pieces, so no bar is left out. 개수 stays the 철근표 count; the piece count is kept beside it. The
삿갓 length h − 100 is an assumption (Q-K5) and is noted on the ④ screen.

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

src/main.ts

@@ -14,7 +14,7 @@ import { rebarSummary, type RebarRow } from './core/rebar/summary';
 import { shearSegments } from './core/rebar/coping';
 import { buildRebar3D, type RebarColorMode, type RebarScene } from './view/rebar3d';
 import { DEFAULT_MATERIAL, FCK_MEMBERS, fyOf, GRADE_CHOICES, isAssumedMaterial, materialFrom, type BendFactors, type FckByMember, type FckMember, type GradeKey, type Material } from './core/rebar/common';
-import { buildQuantity, quantityRows, type Quantity } from './core/rebar/quantity';
+import { buildQuantity, quantityRows, type Quantity, type QuantityLine } from './core/rebar/quantity';
 import { allVisibleChecked, setVisibleChecked, type TypeFilter } from './core/selection';
 import { choose, defaultSummary, isSelectable, SHAPE_GROUPS, UNDEFINED_REASON, type MemberId } from './core/shape-options';
 import { parseProject, SCHEMA_VERSION, serializeProject, type ProjectFile, type ProjectInfo } from './core/project';
@@ -890,7 +890,7 @@ function renderRebar(): void {
       el('td', r.position),
       el('td', r.direction),
       el('td', r.shape),
-      el('td', r.length === null ? '—' : String(Math.round(r.length * 10) / 10)),
+      el('td', r.length === null ? (r.pieces ? '여러 길이' : '—') : String(Math.round(r.length * 10) / 10), undefined),
       el('td', String(r.count)),
       basisCell(r.basis),
       el('td', r.note),
@@ -980,6 +980,14 @@ function quantityTargets(): Pier[] {
   return active?.model ? [active] : [];
 }
 
+/** Length cell of a 재료표 line: the length, or 여러 길이 with the pieces on hover. */
+function lengthCell(l: QuantityLine): HTMLTableCellElement {
+  if (l.length !== null) return el('td', String(l.length));
+  const cell = el('td', `여러 길이 (${l.pieces.length}종)`);
+  cell.title = l.pieces.map((p) => `${Math.round(p.length)} × ${p.count}`).join(' · ');
+  return cell;
+}
+
 function quantityTable(q: Quantity): HTMLTableElement {
   const table = el('table', undefined, 'grid-table rebar-table');
   const head = el('thead');
@@ -993,7 +1001,7 @@ function quantityTable(q: Quantity): HTMLTableElement {
       for (const l of d.lines) {
         body.appendChild(el('tr')).append(
           el('td', `SD${g.grade}`), el('td', l.name, 'bar-no'), el('td', l.shape), el('td', l.size), el('td', String(l.count)),
-          el('td', String(l.length)), el('td', l.totalM.toFixed(1)), el('td', l.kgPerM.toFixed(3)), el('td', l.kg.toFixed(1)),
+          lengthCell(l), el('td', l.totalM.toFixed(1)), el('td', l.kgPerM.toFixed(3)), el('td', l.kg.toFixed(1)),
         );
       }
       body.appendChild(el('tr', undefined, 'subtotal')).append(el('td', ''), el('td', `${d.size} 소계`), el('td', ''), el('td', d.size), el('td', ''), el('td', ''), el('td', d.totalM.toFixed(1)), el('td', ''), el('td', d.kg.toFixed(1)));
@@ -1011,7 +1019,7 @@ function renderQuantityScreen(): void {
   const targets = quantityTargets();
   $('step4-status').textContent = targets.length ? `${targets.length}기` : '예정';
   $('quantity-note').textContent = targets.length
-    ? `${targets.length}기 · 할증 ${state.material.waste}% (기본 0%, 가정). 체크한 교각 기준이고, 체크가 없으면 현재 교각입니다.`
+    ? `${targets.length}기 · 할증 ${state.material.waste}% (기본 0%, 가정). 삿갓 길이는 h − 100으로 가정(Q-K5). 체크한 교각 기준이고, 체크가 없으면 현재 교각입니다.`
     : '계산된 교각이 없습니다. 교각을 생성하세요.';
   let kg = 0;
   let kgWithWaste = 0;