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/31-seo-competitor-intel/desktop/tools/ahrefs.md

@@ -0,0 +1,35 @@
+# Ahrefs
+
+> MCP tool documentation for competitor intelligence skill
+
+## Available Commands
+
+- `site-explorer-metrics` - Get current organic metrics for a domain
+- `site-explorer-metrics-history` - Get historical organic metrics trends
+- `site-explorer-organic-competitors` - Discover organic search competitors
+- `site-explorer-organic-keywords` - Get keyword rankings per domain
+- `site-explorer-top-pages` - Get top performing pages by traffic
+- `site-explorer-pages-by-traffic` - Get pages ranked by organic traffic
+- `site-explorer-domain-rating` - Get Domain Rating score
+- `site-explorer-domain-rating-history` - Get DR trend over time
+- `site-explorer-referring-domains` - Get list of referring domains
+- `site-explorer-backlinks-stats` - Get backlink overview statistics
+- `site-explorer-pages-history` - Get page index history
+
+## Configuration
+
+- Requires Ahrefs MCP server configured in Claude Desktop
+- API access via `mcp__ahrefs__*` tool prefix
+
+## Examples
+
+```
+# Discover competitors
+mcp__ahrefs__site-explorer-organic-competitors(target="example.com")
+
+# Get domain metrics
+mcp__ahrefs__site-explorer-metrics(target="example.com")
+
+# Get keyword rankings
+mcp__ahrefs__site-explorer-organic-keywords(target="example.com", limit=100)
+```