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/README.md

@@ -0,0 +1,80 @@
+# OurDigital Blog
+
+Korean blog draft creation skill for blog.ourdigital.org.
+
+## Purpose
+
+Generate Korean blog posts with:
+- OurDigital brand voice compliance
+- SEO-optimized metadata
+- Ghost CMS format output
+- Ulysses export support
+
+## Activation
+
+Only activates with "ourdigital" keyword:
+- "ourdigital 블로그 써줘"
+- "ourdigital blog 초안"
+- "ourdigital 한국어 포스트 [주제]"
+
+## Channel Profile
+
+| Field | Value |
+|-------|-------|
+| URL | blog.ourdigital.org |
+| Language | Korean (전문용어 영문 병기) |
+| Tone | Analytical & Personal |
+| Length | 1,500-3,000자 |
+
+## Structure
+
+```
+02-ourdigital-blog/
+├── code/SKILL.md
+├── desktop/SKILL.md
+├── shared/
+│   ├── references/
+│   │   └── blog-style-guide.md
+│   ├── templates/
+│   │   └── blog-template.md
+│   └── scripts/
+│       └── ghost_publish.py
+├── docs/
+│   └── CHANGELOG.md
+└── README.md
+```
+
+## Usage
+
+### Draft a Blog Post
+
+```
+User: ourdigital 블로그 써줘 - AI 마케팅 자동화에 대해
+Claude: [Asks clarifying questions, generates draft]
+```
+
+### Publish to Ghost
+
+```bash
+python shared/scripts/ghost_publish.py --file post.md --draft
+```
+
+## Writing Style
+
+- **철학-기술 융합**: 기술 분석 + 인간적 함의
+- **역설 활용**: 긴장/모순으로 논증
+- **수사적 질문**: 독자 참여 유도
+- **전문용어 병기**: 한글(영문)
+
+## Environment
+
+Requires `~/.env.ourdigital`:
+```
+GHOST_BLOG_URL=https://blog.ourdigital.org
+GHOST_BLOG_ADMIN_KEY=<admin_key>
+```
+
+## Version
+
+- Current: 1.0.0
+- Author: OurDigital