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/20-seo-serp-analysis/desktop/tools/ahrefs.md

@@ -1,15 +1,24 @@
-# Ahrefs
+# Ahrefs MCP
 
-> TODO: Document tool usage for this skill
+Use when the user explicitly wants Ahrefs' SERP view, or already has an Ahrefs project for the domain. Namespace: `mcp__ahrefs__*` (Desktop) / `mcp__claude_ai_Ahrefs__*` (Claude.ai) — same backend.
 
-## Available Commands
+## Key endpoints
 
-- [ ] List commands
+- `serp-overview` — top organic, SERP features, paid layout for a keyword
+- `rank-tracker-serp-overview` — SERP layout for keywords in a tracked project
+- `keywords-explorer-overview` — pairs with SERP for SERP-feature signals (Featured Snippet, PAA)
 
-## Configuration
+## Example
 
-- [ ] Add configuration details
+```
+mcp__ahrefs__serp-overview(keyword="<keyword>", country="us")
+mcp__ahrefs__serp-overview(keyword="<keyword>", country="kr")
+```
 
-## Examples
+## Not for this skill when
 
-- [ ] Add usage examples
+- **Naver SERP** — Ahrefs doesn't cover Naver. Use `our research naver serp`.
+- **Single-keyword position spot-check** — `mcp__ourseo__check_serp` is cheaper.
+- **Full SERP JSON with all features for export** — DataForSEO via `our serp live`.
+
+Reference: call `mcp__ahrefs__doc` once per session before first use.

custom-skills/20-seo-serp-analysis/desktop/tools/ourseo.md

@@ -0,0 +1,39 @@
+# OurSEO Agent (CLI + MCP)
+
+Two paths for SERP work:
+
+1. **CLI** (Claude Code, Bash) — `our serp *` (DataForSEO Google) + `our research naver serp` (Naver-only).
+2. **MCP** (Claude Desktop) — `mcp__ourseo__check_serp` for single-keyword spot-check.
+
+## CLI commands
+
+```bash
+# Google SERP via DataForSEO
+our serp live "<keyword>" --location 2410 --language ko
+our serp competitors <domain> --location 2410
+our serp ranked-keywords <domain> --location 2410 --limit 50
+our serp domain-overview <domain> --location 2410
+
+# Naver SERP (Korean engines — Naver-only path)
+our research naver serp "<keyword>"
+our research naver serp "<keyword>" --domain <target.com>
+```
+
+Location codes: `2410` Korea, `2840` US, `2392` Japan.
+
+## MCP tool
+
+```
+mcp__ourseo__check_serp(keyword="<keyword>", domain="<target>", country="kr")
+```
+
+## Strengths
+
+- **Only** path that covers Naver SERP (blog, cafe, knowledge iN, Smart Store, brand zone, shortform, influencer).
+- Cheapest per call for batch Korean-market SERP work.
+- Full live SERP JSON with all features for export.
+
+## Not for this skill when
+
+- **Modelled SERP overview** (volume + CPC trend per keyword) — Semrush is cleanest for that.
+- **Brand Radar / AI search SERP** — Ahrefs Brand Radar is the only option.

custom-skills/20-seo-serp-analysis/desktop/tools/semrush.md

@@ -0,0 +1,28 @@
+# Semrush MCP
+
+Default backend for Google SERP overview, organic competitor positions, SERP-feature presence.
+
+Call pattern: discovery → `get_report_schema` → `execute_report`.
+
+## Key reports (SERP toolkit)
+
+- Domain overview (organic positions, traffic, distribution)
+- Position changes (new/lost/improved/declined)
+- Organic competitors per keyword
+- SERP-feature presence per keyword
+
+## Example
+
+```
+mcp__semrush__overview_research(query="<keyword>", database="us")
+mcp__semrush__get_report_schema(report_id="<id from above>")
+mcp__semrush__execute_report(report_id="<id>", params={"phrase": "<keyword>", "database": "us"})
+```
+
+Korean market: `database="kr"`. Default `database="us"` per Semrush MCP instructions.
+
+## Not for this skill when
+
+- **Naver SERP** — Semrush is Google-only. Use `our research naver serp`.
+- **Raw SERP JSON for parsing all features** (PAA list, video carousel items, image pack) — DataForSEO via `our serp live` exposes richer JSON.
+- **Backlink graph for ranking pages** — Ahrefs `site-explorer-*` is stronger.