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/19-seo-technical-audit/desktop/SKILL.md

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+# SEO Technical Audit
+
+## Purpose
+
+Analyze crawlability fundamentals: robots.txt rules, XML sitemap structure, and URL accessibility. Identify issues blocking search engine crawlers.
+
+## Core Capabilities
+
+1. **Robots.txt Analysis** - Parse rules, check blocked resources
+2. **Sitemap Validation** - Verify XML structure, URL limits, dates
+3. **URL Accessibility** - Check HTTP status, redirects, broken links
+
+## MCP Tool Usage
+
+### Firecrawl for Page Data
+```
+mcp__firecrawl__scrape: Fetch robots.txt and sitemap content
+mcp__firecrawl__crawl: Check multiple URLs accessibility
+```
+
+### Perplexity for Best Practices
+```
+mcp__perplexity__search: Research current SEO recommendations
+```
+
+## Workflow
+
+### 1. Robots.txt Check
+1. Fetch `[domain]/robots.txt` using Firecrawl
+2. Parse User-agent rules and Disallow patterns
+3. Identify blocked resources (CSS, JS, images)
+4. Check for Sitemap declarations
+5. Report critical issues
+
+### 2. Sitemap Validation
+1. Locate sitemap (from robots.txt or `/sitemap.xml`)
+2. Validate XML syntax
+3. Check URL count (max 50,000)
+4. Verify lastmod date formats
+5. For sitemap index: parse child sitemaps
+
+### 3. URL Accessibility Sampling
+1. Extract URLs from sitemap
+2. Sample 50-100 URLs for large sites
+3. Check HTTP status codes
+4. Identify redirects and broken links
+5. Report 4xx/5xx errors
+
+## Output Format
+
+```markdown
+## Technical SEO Audit: [domain]
+
+### Robots.txt Analysis
+- Status: [Valid/Invalid/Missing]
+- Sitemap declared: [Yes/No]
+- Critical blocks: [List]
+
+### Sitemap Validation
+- URLs found: [count]
+- Syntax: [Valid/Errors]
+- Issues: [List]
+
+### URL Accessibility (sampled)
+- Checked: [count] URLs
+- Success (2xx): [count]
+- Redirects (3xx): [count]
+- Errors (4xx/5xx): [count]
+
+### Recommendations
+1. [Priority fixes]
+```
+
+## Common Issues
+
+| Issue | Impact | Fix |
+|-------|--------|-----|
+| No sitemap in robots.txt | Medium | Add `Sitemap:` directive |
+| Blocking CSS/JS | High | Allow Googlebot access |
+| 404s in sitemap | High | Remove or fix URLs |
+| Missing lastmod | Low | Add dates for freshness signals |
+
+## Limitations
+
+- Cannot access password-protected sitemaps
+- Large sitemaps (10,000+ URLs) require sampling
+- Does not check render-blocking issues (use Core Web Vitals skill)
+
+## Notion Output (Required)
+
+All audit reports MUST be saved to OurDigital SEO Audit Log:
+- **Database ID**: `2c8581e5-8a1e-8035-880b-e38cefc2f3ef`
+- **Properties**: Issue (title), Site (url), Category, Priority, Found Date, Audit ID
+- **Language**: Korean with English technical terms
+- **Audit ID Format**: [TYPE]-YYYYMMDD-NNN
+

custom-skills/19-seo-technical-audit/desktop/skill.yaml

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+# Skill metadata (extracted from SKILL.md frontmatter)
+
+name: seo-technical-audit
+description: |
+  Technical SEO auditor for crawlability fundamentals. Triggers: robots.txt, sitemap validation, crawlability, indexing check, technical SEO.
+
+# Optional fields
+allowed-tools:
+  - mcp__firecrawl__*
+  - mcp__perplexity__*
+  - mcp__notion__*
+
+# triggers: []  # TODO: Extract from description

custom-skills/19-seo-technical-audit/desktop/tools/firecrawl.md

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+# Firecrawl
+
+> TODO: Document tool usage for this skill
+
+## Available Commands
+
+- [ ] List commands
+
+## Configuration
+
+- [ ] Add configuration details
+
+## Examples
+
+- [ ] Add usage examples

custom-skills/19-seo-technical-audit/desktop/tools/notion.md

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+# Notion
+
+> TODO: Document tool usage for this skill
+
+## Available Commands
+
+- [ ] List commands
+
+## Configuration
+
+- [ ] Add configuration details
+
+## Examples
+
+- [ ] Add usage examples

custom-skills/19-seo-technical-audit/desktop/tools/perplexity.md

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+# Perplexity
+
+> TODO: Document tool usage for this skill
+
+## Available Commands
+
+- [ ] List commands
+
+## Configuration
+
+- [ ] Add configuration details
+
+## Examples
+
+- [ ] Add usage examples