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/README.md

@@ -0,0 +1,71 @@
+# OurDigital Journal
+
+English essay and article creation skill for journal.ourdigital.org.
+
+## Purpose
+
+Generate English essays with:
+- Reflective, poetic writing style
+- Philosophical-technical hybridization
+- Cultural bridging (Korean-global perspectives)
+- Ghost CMS format output
+
+## Activation
+
+Only activates with "ourdigital" keyword:
+- "ourdigital journal 써줘"
+- "ourdigital English essay on [topic]"
+- "ourdigital 영문 에세이"
+
+## Channel Profile
+
+| Field | Value |
+|-------|-------|
+| URL | journal.ourdigital.org |
+| Language | English |
+| Tone | Conversational, Poetic, Reflective |
+| Length | 1,000-2,000 words |
+
+## Structure
+
+```
+03-ourdigital-journal/
+├── code/SKILL.md
+├── desktop/SKILL.md
+├── shared/
+│   ├── references/
+│   │   └── journal-style-guide.md
+│   └── templates/
+│       └── essay-template.md
+├── docs/
+│   └── CHANGELOG.md
+└── README.md
+```
+
+## Writing Style
+
+- **Philosophical-Technical Hybridization**: Tech + human implications
+- **Paradox as Device**: Illuminate through tensions
+- **Rhetorical Questions**: Invite rather than lecture
+- **Melancholic Optimism**: Clear-eyed hope
+
+## Content Types
+
+| Type | Focus | Length |
+|------|-------|--------|
+| Personal Essay | Reflection on experience | 1,000-1,500 words |
+| Cultural Observation | Tech + society | 1,500-2,000 words |
+| Industry Insight | Trends with depth | 1,200-1,800 words |
+
+## Environment
+
+Requires `~/.env.ourdigital`:
+```
+GHOST_JOURNAL_URL=https://journal.ourdigital.org
+GHOST_JOURNAL_ADMIN_KEY=<admin_key>
+```
+
+## Version
+
+- Current: 1.0.0
+- Author: OurDigital