fix(core): replace abolished E04 with I02 in the unimplemented list

E04 (fck 미입력 차단) was abolished on 2026-10-22; fck and fy are now inputs
with assumed defaults, reported as I02 in the rebar stage (spec §10, §13 Q8).

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

src/core/validate.ts

@@ -5,7 +5,7 @@ const EXPECTED_COLUMNS: Record<PierType, number> = { 'T형': 1, '2주형': 2, '3
 
 /** Rules from spec §10 that are not implemented in this stage. Shown to the user, never silently skipped. */
 export const NOT_IMPLEMENTED_RULES = [
-  'E04 fck 미입력 (배근 단계, 3단계)',
+  'I02 fck·fy가 기본값(가정) 그대로 (③ 배근 단계, 3단계)',
   'W06 속성 복사 건너뜀 (2단계)',
   'W08 솔플레이트 T1−T2 검사 (2단계)',
 ] as const;