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/04-ourdigital-research/README.md

@@ -0,0 +1,77 @@
+# OurDigital Research
+
+Deep research and structured prompt generation skill for OurDigital workflows.
+
+## Purpose
+
+Transform questions into:
+- Comprehensive research papers
+- Structured research prompts
+- Blog drafts for OurDigital channels
+- Notion-archived knowledge
+
+## Activation
+
+Only activates with "ourdigital" keyword:
+- "ourdigital research [topic]"
+- "ourdigital 리서치 해줘"
+- "ourdigital deep research on [topic]"
+
+## Workflow
+
+```
+Phase 1: Discovery
+    ↓
+Phase 2: Research Planning
+    ↓
+Phase 3: Deep Research
+    ↓
+Phase 4: Research Paper
+    ↓
+Phase 5: Notion Save
+    ↓
+Phase 6: Blog Draft (optional)
+    ↓
+Phase 7: Ulysses Export
+```
+
+## Structure
+
+```
+04-ourdigital-research/
+├── code/
+│   ├── SKILL.md
+│   ├── CLAUDE.md (legacy)
+│   ├── scripts/
+│   └── references/
+├── desktop/
+│   ├── SKILL.md
+│   └── skill.yaml
+├── shared/
+│   ├── references/
+│   └── scripts/
+├── docs/
+│   └── CHANGELOG.md
+└── README.md
+```
+
+## Integration
+
+Works with:
+- `02-ourdigital-blog` - Korean blog drafts
+- `03-ourdigital-journal` - English essays
+- Notion "Working with AI" database
+- Ulysses for editing
+
+## Quick Commands
+
+| Command | Action |
+|---------|--------|
+| "ourdigital research [topic]" | Start discovery |
+| "ourdigital research → blog" | Full pipeline |
+| "ourdigital 리서치 프롬프트" | Prompt only |
+
+## Version
+
+- Current: 1.1.0
+- Author: OurDigital