feat: install korean technical blog skill bundle

.agents/skills의 technical-document-author,
revising-korean-technical-prose, writing-natural-korean을
korean-technical-blog-skills-bundle-v1의 세 스킬로 교체한다.

- writing-korean-technical-blogs: 문제·제약·선택·구현·결과·한계 구조화
- reducing-ai-like-korean-writing: 상투성·추상화·반복 제거
- editing-korean-grammar-and-expression: 맞춤법·띄어쓰기·호응 검수

상류를 수정하지 않고 복사했다. diff -r 0건, MANIFEST.sha256 검증 통과,
번들 validate_skill.py 3/3 PASS.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.agents/skills/writing-korean-technical-blogs/profiles/migration-case-study.yaml

@@ -0,0 +1,17 @@
+id: migration-case-study
+register: preserve_or_hamnida
+use_when: 데이터, 플랫폼, 프레임워크, 인프라 또는 API 이관 과정을 설명할 때
+required_sections:
+  - why_migration_was_needed
+  - source_and_target_constraints
+  - migration_strategy
+  - validation_and_rollback
+  - rollout
+  - result_and_remaining_risk
+optional_sections:
+  - data_backfill
+  - compatibility_layer
+  - operational_checklist
+rules:
+  explain_invisible_work_value_early: true
+  preserve_failure_and_rollback_conditions: true