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>

.claude/commands/gtm-manager.md

@@ -20,15 +20,15 @@ Full GTM management with dataLayer injection and tag generation.
 
 ```bash
 # Full GTM management
-python ourdigital-custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
+python custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
   --url https://example.com --full-audit
 
 # Generate dataLayer tag
-python ourdigital-custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
+python custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
   --generate-tag purchase --output purchase_tag.html
 
 # Export to Notion
-python ourdigital-custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
+python custom-skills/21-gtm-manager/code/scripts/gtm_manager.py \
   --url https://example.com --notion-export --database DATABASE_ID
 ```