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/03-ourdigital-journal/code/SKILL.md

@@ -0,0 +1,128 @@
+---
+name: ourdigital-journal
+description: |
+  English essay creation for journal.ourdigital.org.
+  Activated with "ourdigital" keyword.
+
+  Triggers:
+  - "ourdigital journal", "ourdigital essay"
+  - "ourdigital English article"
+
+  Features:
+  - English essay generation
+  - Reflective, poetic style
+  - Ghost CMS export
+version: "1.0"
+author: OurDigital
+environment: Code
+---
+
+# OurDigital Journal (Code)
+
+English essay and article creation with Ghost CMS integration.
+
+## Activation
+
+Only with "ourdigital" keyword:
+- "ourdigital journal 써줘"
+- "ourdigital English essay"
+
+## Quick Start
+
+```bash
+# Export to Ghost (draft)
+python shared/scripts/ghost_publish.py --file essay.md --channel journal --draft
+```
+
+## Channel Profile
+
+```yaml
+URL: journal.ourdigital.org
+Language: English
+Tone: Conversational, Poetic, Reflective
+Platform: Ghost CMS
+Length: 1,000-2,000 words
+Frequency: 월 2-4회
+```
+
+## Workflow
+
+### 1. Topic Exploration
+
+Ask:
+1. What specific angle interests you?
+2. Target audience? (Tech pros / General / Academic)
+3. Depth level? (Reflection / Analysis / Observation)
+
+### 2. Essay Structure
+
+```
+1. Opening (Evocative scene or question)
+2. Exploration (3-4 interconnected observations)
+3. Synthesis (Weaving threads)
+4. Closing (Open-ended reflection)
+```
+
+### 3. Writing Style
+
+| Element | Approach |
+|---------|----------|
+| Voice | First-person, reflective |
+| Tone | Thoughtful, observant |
+| Sentences | Complex, interconnected |
+| Questions | Rhetorical, inviting |
+
+### 4. Distinctive Qualities
+
+- Philosophical-technical hybridization
+- Paradox as rhetorical device
+- Epistemic humility
+- Cultural bridging
+
+### 5. Output
+
+```markdown
+---
+title: "Essay Title"
+meta_description: "Description"
+slug: "url-slug"
+tags: ["tag1", "tag2"]
+---
+
+# Essay Title
+
+[Essay content]
+```
+
+## Ghost Integration
+
+```python
+# Environment
+GHOST_JOURNAL_URL=https://journal.ourdigital.org
+GHOST_JOURNAL_ADMIN_KEY=<from .env.ourdigital>
+```
+
+## Export Options
+
+1. **Ghost Draft** → API push
+2. **Local** → `./output/journal/`
+
+## Content Types
+
+| Type | Length |
+|------|--------|
+| Personal Essay | 1,000-1,500 words |
+| Cultural Observation | 1,500-2,000 words |
+| Industry Insight | 1,200-1,800 words |
+
+## File Structure
+
+```
+03-ourdigital-journal/
+├── code/SKILL.md
+├── desktop/SKILL.md
+├── shared/
+│   ├── references/journal-style-guide.md
+│   └── templates/essay-template.md
+└── docs/CHANGELOG.md
+```