feat(ground): 지반·지층 card inputs, layer rows, water level, section drawing

- types/ground.ts: 위치 (육상·하상·해상), 지하수위 고려 and EL, 지층 행
  (name and 하단 EL, from the top down). Checks G01 (layer order), G02 (water
  level range), G03 (layer name).
- The 지반고 still feeds the soil cover check; the layer rows and water level
  are inputs and do not change the 3D model.
- view/ground-svg.ts: the 삽도 drawn from the inputs and the generated
  footings and piles on one EL scale.
- 일괄 적용 copies 위치 and 지하수위 to the checked piers (속성 복사 item,
  off by default). Changes list shows arrays and booleans as text.

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

src/core/copy.ts

@@ -5,7 +5,7 @@ import type { PierInput } from './types';
  * 속성 복사 (spec §9 · plan C7). Copies chosen attributes from one pier to others.
  * Values the spec never copies (coordinates, IP, elevations, names) are not in any item, so they cannot be copied.
  */
-export type CopyItem = 'coping-width' | 'coping-length' | 'pile-length' | 'pile-rows';
+export type CopyItem = 'coping-width' | 'coping-length' | 'pile-length' | 'pile-rows' | 'ground-position';
 
 interface ItemRule {
   label: string;
@@ -21,6 +21,7 @@ export const COPY_ITEMS: Record<CopyItem, ItemRule> = {
   'coping-length': { label: '코핑 길이 L', keys: ['copingLengthMm'], defaultOn: false, pileItem: false },
   'pile-length': { label: '말뚝 길이', keys: ['pileLengthMm'], defaultOn: false, pileItem: true },
   'pile-rows': { label: '열별 본수', keys: ['pileRows'], defaultOn: false, pileItem: true },
+  'ground-position': { label: '지반 위치·지하수위', keys: ['groundPosition', 'groundWaterOn', 'groundWaterEl'], defaultOn: false, pileItem: false },
 };
 
 export const DEFAULT_COPY_ITEMS: CopyItem[] = (Object.keys(COPY_ITEMS) as CopyItem[]).filter((k) => COPY_ITEMS[k].defaultOn);