feat(view,rebar): column diameter D as a free input on ② (1200–3000 mm, 50 mm steps), with three checks

D is an input on the column card (default 2000 mm). The 3D column, the piles of a cast-in pier and the column rebar follow it;
n_div stays 46. Three checks run on each regenerate and appear in 알림: D below the Level width (2100), D + 2c within the
coping width, and the 주철근 arc spacing ≥ max(1.5·d_b, 40). Spec §5.2 records the rule (approved 2026-10-23).

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

src/core/changes.ts

@@ -7,6 +7,7 @@ import type { PierInput } from './types';
 export const EDITABLE_FIELDS = [
   { key: 'copingWidthMm', label: '코핑 폭 B', unit: 'mm' },
   { key: 'copingLengthMm', label: '코핑 길이 L', unit: 'mm' },
+  { key: 'columnDiameterMm', label: '기둥 직경 D', unit: 'mm' },
   { key: 'copingH1Mm', label: '끝단 높이 h1', unit: 'mm' },
   { key: 'copingH2Mm', label: '테이퍼 높이 h2', unit: 'mm' },
   { key: 'levelWidthMm', label: 'Level 폭', unit: 'mm' },
@@ -21,6 +22,7 @@ export type EditableKey = (typeof TRACKED_KEYS)[number];
 export const FIELD_LABELS: Record<EditableKey, string> = {
   copingWidthMm: '코핑 폭 B',
   copingLengthMm: '코핑 길이 L',
+  columnDiameterMm: '기둥 직경 D',
   copingH1Mm: '끝단 높이 h1',
   copingH2Mm: '테이퍼 높이 h2',
   levelWidthMm: 'Level 폭',