Add SEO skills 19-28, 31-32 with full Python implementations

12 new skills: Keyword Strategy, SERP Analysis, Position Tracking,
Link Building, Content Strategy, E-Commerce SEO, KPI Framework,
International SEO, AI Visibility, Knowledge Graph, Competitor Intel,
and Crawl Budget. ~20K lines of Python across 25 domain scripts.
Updated skill 11 pipeline table and repo CLAUDE.md.
Enhanced skill 18 local SEO workflow from jamie.clinic audit.

Note: Skill 26 hreflang_validator.py pending (content filter block).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

custom-skills/22-seo-link-building/desktop/SKILL.md

@@ -0,0 +1,116 @@
+---
+name: seo-link-building
+description: |
+  Link building diagnosis and backlink analysis tool.
+  Triggers: backlink audit, link building, referring domains, toxic links, link gap, broken backlinks, 백링크 분석, 링크빌딩.
+---
+
+# SEO Link Building Diagnosis
+
+## Purpose
+
+Analyze backlink profiles, detect toxic links, find competitor link gaps, track link velocity, and map Korean platform links. Provides actionable link building recommendations.
+
+## Core Capabilities
+
+1. **Backlink Profile Audit** - DR, referring domains, dofollow ratio, anchor distribution
+2. **Toxic Link Detection** - PBN patterns, spam domains, link farm identification
+3. **Competitor Link Gap Analysis** - Domains linking to competitors but not target
+4. **Link Velocity Tracking** - New/lost referring domains over time
+5. **Broken Backlink Recovery** - Find and reclaim broken high-DR backlinks
+6. **Korean Platform Mapping** - Naver Blog, Cafe, Tistory, Brunch, Korean news
+
+## MCP Tool Usage
+
+### Ahrefs for Backlink Data
+```
+mcp__ahrefs__site-explorer-all-backlinks: Get all backlinks for a target
+mcp__ahrefs__site-explorer-backlinks-stats: Backlink statistics overview
+mcp__ahrefs__site-explorer-referring-domains: List referring domains
+mcp__ahrefs__site-explorer-anchors: Anchor text distribution
+mcp__ahrefs__site-explorer-broken-backlinks: Find broken backlinks
+mcp__ahrefs__site-explorer-domain-rating: Get Domain Rating
+mcp__ahrefs__site-explorer-domain-rating-history: DR trend over time
+mcp__ahrefs__site-explorer-refdomains-history: Referring domains trend
+mcp__ahrefs__site-explorer-linked-domains: Domains linked from target
+```
+
+### Notion for Report Storage
+```
+mcp__notion__notion-create-pages: Save audit report to SEO Audit Log
+mcp__notion__notion-update-page: Update existing audit entries
+```
+
+## Workflow
+
+### 1. Backlink Profile Audit
+1. Fetch Domain Rating via `site-explorer-domain-rating`
+2. Get backlink stats via `site-explorer-backlinks-stats`
+3. Retrieve referring domains via `site-explorer-referring-domains`
+4. Analyze anchor distribution via `site-explorer-anchors`
+5. Detect toxic links (PBN patterns, spam keywords, suspicious TLDs)
+6. Map Korean platform links from referring domains
+7. Report with issues and recommendations
+
+### 2. Link Gap Analysis
+1. Fetch target referring domains
+2. Fetch competitor referring domains (parallel)
+3. Compute set difference (competitor - target)
+4. Score opportunities by DR, traffic, category
+5. Categorize sources (news, blog, forum, directory, Korean platform)
+6. Rank by feasibility and impact
+7. Report top opportunities with recommendations
+
+### 3. Link Velocity Check
+1. Fetch refdomains-history for last 90 days
+2. Calculate new/lost referring domains per period
+3. Determine velocity trend (growing/stable/declining)
+4. Flag declining velocity as issue
+
+### 4. Broken Backlink Recovery
+1. Fetch broken backlinks via `site-explorer-broken-backlinks`
+2. Sort by DR (highest value first)
+3. Recommend 301 redirects or content recreation
+
+## Output Format
+
+```markdown
+## Link Building Audit: [domain]
+
+### Overview
+- Domain Rating: [DR]
+- Referring Domains: [count]
+- Dofollow Ratio: [ratio]
+- Toxic Links: [count] ([risk level])
+
+### Anchor Distribution
+| Type | Count | % |
+|------|-------|---|
+| Branded | [n] | [%] |
+| Exact Match | [n] | [%] |
+| Generic | [n] | [%] |
+| Naked URL | [n] | [%] |
+
+### Toxic Links (Top 10)
+| Domain | Risk Score | Reason |
+|--------|-----------|--------|
+
+### Korean Platform Links
+| Platform | Count |
+|----------|-------|
+
+### Link Velocity
+| Period | New | Lost |
+|--------|-----|------|
+
+### Recommendations
+1. [Priority actions]
+```
+
+## 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 (Link Building), Priority, Found Date, Audit ID
+- **Language**: Korean with English technical terms
+- **Audit ID Format**: LINK-YYYYMMDD-NNN