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/_ourdigital-shared/requirements/code.txt

@@ -0,0 +1,23 @@
+# OurDigital Skills - Claude Code Requirements
+# Dependencies specific to Claude Code environment
+
+-r base.txt
+
+# Anthropic SDK (for programmatic Claude access)
+anthropic>=0.18.0
+
+# Ghost CMS integration
+# ghost-admin-api>=0.1.0  # If available, or use requests
+
+# SEO tools
+beautifulsoup4>=4.12.0
+lxml>=4.9.0
+
+# Web scraping (for research skills)
+aiohttp>=3.9.0
+
+# Data analysis
+pandas>=2.1.0
+
+# Template rendering
+jinja2>=3.1.0