feat: Add OurDigital custom skills package (10 skills)

Complete implementation of OurDigital skills with dual-platform support
(Claude Desktop + Claude Code) following standardized structure.

Skills created:
- 01-ourdigital-brand-guide: Brand reference & style guidelines
- 02-ourdigital-blog: Korean blog drafts (blog.ourdigital.org)
- 03-ourdigital-journal: English essays (journal.ourdigital.org)
- 04-ourdigital-research: Research prompts & workflows
- 05-ourdigital-document: Notion-to-presentation pipeline
- 06-ourdigital-designer: Visual/image prompt generation
- 07-ourdigital-ad-manager: Ad copywriting & keyword research
- 08-ourdigital-trainer: Training materials & workshop planning
- 09-ourdigital-backoffice: Quotes, proposals, cost analysis
- 10-ourdigital-skill-creator: Meta skill for creating new skills

Features:
- YAML frontmatter with "ourdigital" or "our" prefix triggers
- Standardized directory structure (code/, desktop/, shared/, docs/)
- Shared environment setup (_ourdigital-shared/)
- Comprehensive reference documentation
- Cross-skill integration support

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

custom-skills/02-ourdigital-blog/code/SKILL.md

@@ -0,0 +1,147 @@
+---
+name: ourdigital-blog
+description: |
+  Korean blog drafting for blog.ourdigital.org.
+  Activated with "ourdigital" keyword.
+
+  Triggers:
+  - "ourdigital 블로그", "ourdigital blog"
+  - "ourdigital 한국어 포스트"
+
+  Features:
+  - Korean blog draft generation
+  - SEO metadata creation
+  - Ghost CMS export
+  - Ulysses integration
+version: "1.0"
+author: OurDigital
+environment: Code
+---
+
+# OurDigital Blog (Code)
+
+Korean blog draft creation with Ghost CMS integration.
+
+## Activation
+
+Only with "ourdigital" keyword:
+- "ourdigital 블로그 써줘"
+- "ourdigital blog 초안"
+
+## Quick Start
+
+```bash
+# Export to Ulysses
+python shared/scripts/export_blog.py --output ulysses
+
+# Push to Ghost (draft)
+python shared/scripts/ghost_publish.py --draft
+```
+
+## Channel Profile
+
+```yaml
+URL: blog.ourdigital.org
+Language: Korean (영문 전문용어 병기)
+Tone: Analytical, Educational
+Platform: Ghost CMS
+Length: 1,500-3,000자
+Frequency: 주 1-2회
+```
+
+## Workflow
+
+### 1. Topic Clarification
+
+Ask:
+1. 주제가 무엇인가요?
+2. 타겟 독자는? (마케터/개발자/일반)
+3. 깊이 수준? (개요/심층/실무가이드)
+
+### 2. Draft Structure
+
+```
+1. 도입부 (Hook + Context)
+2. 본론 (3-5 핵심 포인트)
+   - 주장 → 근거 → 함의
+3. 결론 (Summary + 열린 질문)
+```
+
+### 3. Writing Style
+
+| Element | Rule |
+|---------|------|
+| Tone | 분석적 + 개인적 |
+| Language | 한글 기본, 전문용어 영문 병기 |
+| Structure | 관찰 → 분석 → 함의 |
+| Questions | 수사적 질문으로 참여 유도 |
+
+### 4. SEO Metadata
+
+Generate:
+```yaml
+title: [60자 이내]
+meta_description: [155자 이내]
+slug: english-url-slug
+tags: [tag1, tag2, tag3]
+```
+
+### 5. Output
+
+**Markdown format:**
+```markdown
+---
+title: "제목"
+meta_description: "설명"
+slug: "url-slug"
+tags: ["tag1", "tag2"]
+---
+
+# 제목
+
+[본문]
+```
+
+## Ghost Integration
+
+```python
+# Environment variables
+GHOST_BLOG_URL=https://blog.ourdigital.org
+GHOST_BLOG_ADMIN_KEY=<from .env.ourdigital>
+```
+
+## Export Options
+
+1. **Ulysses** → `$ULYSSES_EXPORT_PATH`
+2. **Ghost Draft** → API push
+3. **Local** → `./output/blog/`
+
+## Brand Compliance
+
+Verify before export:
+- ✓ 분석적 톤
+- ✓ 기술 + 인간적 함의
+- ✓ 전문용어 영문 병기
+- ✓ 1,500-3,000자
+
+## Scripts
+
+| Script | Purpose |
+|--------|---------|
+| `export_blog.py` | Export to various targets |
+| `ghost_publish.py` | Push to Ghost CMS |
+
+## File Structure
+
+```
+02-ourdigital-blog/
+├── code/SKILL.md
+├── desktop/SKILL.md
+├── shared/
+│   ├── references/blog-style-guide.md
+│   ├── templates/blog-template.md
+│   └── scripts/
+│       ├── export_blog.py
+│       └── ghost_publish.py
+└── docs/CHANGELOG.md
+```