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/06-ourdigital-designer/code/CLAUDE.md

@@ -0,0 +1,74 @@
+# CLAUDE.md
+
+## Overview
+
+Visual storytelling toolkit for OurDigital blog featured images. Creates sophisticated image prompts that capture philosophical depth through minimalist visual metaphors.
+
+## Quick Start
+
+```bash
+# Generate image prompt
+python scripts/generate_prompt.py --topic "AI identity" --mood "contemplative"
+
+# Calibrate mood parameters
+python scripts/mood_calibrator.py --input "essay excerpt" --style "minimalist"
+```
+
+## Scripts
+
+| Script | Purpose |
+|--------|---------|
+| `generate_prompt.py` | Generate AI image prompts from essay concepts |
+| `mood_calibrator.py` | Calibrate emotional parameters for consistency |
+
+## Prompt Generator
+
+```bash
+# Basic generation
+python scripts/generate_prompt.py --topic "AI identity crisis"
+
+# With mood and metaphor
+python scripts/generate_prompt.py \
+  --topic "AI identity crisis" \
+  --mood "contemplative anxiety" \
+  --metaphor "mirror fragments"
+
+# From essay text
+python scripts/generate_prompt.py --input essay.txt --auto-extract
+```
+
+## Mood Calibrator
+
+```bash
+# Analyze text for emotional tone
+python scripts/mood_calibrator.py --input "essay text"
+
+# Adjust existing prompt
+python scripts/mood_calibrator.py \
+  --prompt "existing prompt" \
+  --adjust-warmth 0.3 \
+  --adjust-complexity -0.2
+```
+
+## Output Format
+
+Generated prompts follow OurDigital style:
+- 1200x630px dimensions (OG standard)
+- Minimalist vector + subtle textures
+- 60-30-10 color rule
+- 20%+ negative space
+
+## References
+
+See `references/` for:
+- `visual_metaphors.md` - Concept to visual mapping
+- `color_palettes.md` - Emotion to color mapping
+- `advanced_techniques.md` - Style guidelines
+
+## Visual Approaches by Essay Type
+
+| Type | Strategy | Colors |
+|------|----------|--------|
+| Technology | Organic-digital hybrids | Cool blues → warm accents |
+| Social | Network patterns | Desaturated → hope spots |
+| Philosophy | Zen space, symbols | Monochrome + single accent |