feat(seo-skills): multi-backend Data Source Selection (#7)

Replaces single-vendor (Ahrefs-only) tool defaults with a per-task
backend menu across all 14 SEO skills. Each skill now lists every
capable MCP in allowed-tools and documents how to pick between
Semrush, Ahrefs, OurSEO Agent (CLI + MCP), DataForSEO, and GSC
in its SKILL.md Data Source Selection section.

Tool stubs (~40 new files) populated per skill with capability
deltas, call patterns, and explicit "not for this skill when"
callouts so the menu is self-correcting.

Skills affected: 19-keyword-strategy, 20-serp-analysis,
21-position-tracking, 22-link-building, 23-content-strategy,
24-ecommerce, 25-kpi-framework, 26-international, 27-ai-visibility,
28-knowledge-graph, 31-competitor-intel, 32-crawl-budget,
33-migration-planner, 34-reporting-dashboard.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/34-seo-reporting-dashboard/desktop/tools/ahrefs.md

@@ -1,20 +1,51 @@
-# Ahrefs
+# Ahrefs MCP
 
-Tools used for pulling fresh SEO data into the reporting dashboard.
+In the reporting dashboard, Ahrefs is the source for **backlinks**, **DR + history**, **traffic-value alternate**, **Brand Radar AI visibility**, and **per-country traffic** breakouts.
 
-## Tools Used
+Namespace: `mcp__ahrefs__*` / `mcp__claude_ai_Ahrefs__*`.
 
-| Tool | Purpose |
-|------|---------|
-| `mcp__ahrefs__site-explorer-metrics` | Current organic metrics snapshot (traffic, keywords, DR) |
-| `mcp__ahrefs__site-explorer-metrics-history` | Historical metrics for trend charts and period comparison |
+## Tools used in dashboard sections
 
-## Usage
+| Section | Endpoint |
+|---|---|
+| Backlinks / DR | `site-explorer-domain-rating`, `site-explorer-backlinks-stats` |
+| DR trend chart | `site-explorer-domain-rating-history` |
+| Refdomains trend chart | `site-explorer-refdomains-history` |
+| Traffic / visibility snapshot (alternate) | `site-explorer-metrics` |
+| Traffic / visibility trend (alternate) | `site-explorer-metrics-history` |
+| AI search visibility / SOV | `brand-radar-sov-overview`, `brand-radar-sov-history` |
+| Cited pages in AI answers | `brand-radar-cited-pages`, `brand-radar-cited-domains` |
+| Per-country traffic distribution | `web-analytics-countries`, `site-explorer-metrics-by-country` |
+| First-party clicks/impressions (if connected) | `gsc-performance-history`, `gsc-pages-history` |
 
-These tools are called when the dashboard needs fresh data beyond what is available from cached skill outputs. The aggregator first checks local JSON files and Notion audit log entries, then optionally pulls current data from Ahrefs to supplement the report.
+## Example
 
-## Notes
+```
+mcp__ahrefs__site-explorer-metrics(target="<domain>")
+mcp__ahrefs__site-explorer-metrics-history(target="<domain>", history="weekly")
+mcp__ahrefs__brand-radar-sov-overview(brand="<brand>")
+mcp__ahrefs__web-analytics-countries(domain="<domain>")
+```
 
-- Ahrefs data has approximately 24-hour freshness lag
-- Traffic value from Ahrefs is in cents; divide by 100 for USD
-- Historical data availability depends on Ahrefs subscription tier
+## Strengths for the dashboard
+
+- **Pre-computed trend series** — saves the dashboard from synthesizing trends from point-in-time pulls.
+- **Brand Radar is Ahrefs-only** — required for AI-visibility report sections.
+- Traffic value in **USD cents** — divide by 100 for USD when rendering.
+
+## Reporting rule
+
+Whenever an Ahrefs endpoint feeds a section, list it in the report's **Sources** subsection (e.g., `Backlinks / DR: Ahrefs site-explorer-domain-rating`).
+
+## Not for this skill when
+
+- **First-party clicks / impressions / CTR** — prefer GSC over `gsc-*` Ahrefs alternates unless Ahrefs project is already configured.
+- **Technical health section** — OurSEO `audit_page` / `audit tech`.
+- **GA4 sessions / conversions** — `our research ga4 *`.
+- **GBP local KPIs** — `our collect gbp *` / `our audit local`.
+
+Notes:
+- Ahrefs data has ~24h freshness lag.
+- Historical data window depends on Ahrefs subscription tier — fall back to point-in-time + manual snapshot history if needed.
+
+Reference: `mcp__ahrefs__doc` once per session.