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/10-ourdigital-skill-creator/README.md

@@ -0,0 +1,75 @@
+# OurDigital Skill Creator
+
+Meta skill for creating, validating, and managing OurDigital Claude Skills.
+
+## Purpose
+
+This skill helps create new OurDigital skills with:
+- Proper directory structure
+- YAML frontmatter conventions
+- OurDigital trigger patterns
+- Notion history tracking
+
+## Activation
+
+Only activates with "ourdigital" keyword:
+- "ourdigital 스킬 만들기"
+- "ourdigital skill creator"
+- "create ourdigital skill"
+
+## Structure
+
+```
+10-ourdigital-skill-creator/
+├── code/
+│   └── SKILL.md              # Claude Code version
+├── desktop/
+│   └── SKILL.md              # Claude Desktop version
+├── shared/
+│   ├── references/
+│   │   ├── suitability-criteria.md
+│   │   └── skill-patterns.md
+│   ├── templates/
+│   │   └── SKILL-TEMPLATE.md
+│   └── scripts/
+│       ├── init_skill.py
+│       └── validate_skill.py
+├── docs/
+│   ├── CHANGELOG.md
+│   └── logs/
+└── README.md
+```
+
+## Usage
+
+### Create a New Skill
+
+```bash
+python shared/scripts/init_skill.py {name} --number XX
+
+# Example
+python shared/scripts/init_skill.py blog --number 02
+```
+
+### Validate a Skill
+
+```bash
+python shared/scripts/validate_skill.py {skill-directory}
+
+# Example
+python shared/scripts/validate_skill.py 02-ourdigital-blog
+```
+
+## Workflow
+
+1. **Suitability Check** - Evaluate if need fits Claude Skill criteria
+2. **Requirements Q&A** - Gather purpose, triggers, tools, outputs
+3. **Generate Structure** - Create directories and files
+4. **Validation** - Verify structure and content
+5. **Notion Sync** - Record to Working with AI database
+
+## Version
+
+- Current: 1.0.0
+- Author: OurDigital
+- Environment: Both (Desktop & Code)