feat(commands): add /seo-auditor — 7-phase SEO audit pipeline for documentation

- 7 phases: discovery → meta tags → content quality → keywords → links → sitemap → report
- Integrates 8 marketing-skill scripts: seo_checker, content_scorer,
  humanizer_scorer, headline_scorer, seo_optimizer, sitemap_analyzer,
  schema_validator, topic_cluster_mapper
- References 6 SEO knowledge bases for audit framework, AI search,
  content optimization, URL design, internal linking, AI detection
- Auto-fixes: generic titles, missing descriptions, broken links, orphan pages
- Preserves high-ranking pages — only fixes critical issues on those
- Registered in both commands/ (distributable) and .claude/commands/ (local)

Also: sync all doc counts — 28 plugins, 26 eng-core skills, 21 commands

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/commands/seo-auditor.md

@@ -0,0 +1,97 @@
+---
+description: Scan and optimize docs for SEO — meta tags, readability, keywords, broken links, sitemap.
+---
+
+Run the SEO auditor on documentation files. Target path: `$ARGUMENTS` (default: all docs/ and root README.md).
+
+If `$ARGUMENTS` is `--report-only`, scan without making changes.
+
+Execute all 7 phases. Auto-fix non-destructive issues. Never change URLs. Preserve content on high-ranking pages.
+
+## Phase 1: Discovery
+
+Find all target markdown files:
+- `docs/**/*.md` — all documentation pages
+- `README.md` files in domain root directories
+- If `$ARGUMENTS` specifies a path, scope to that path only
+
+For each file, extract current state: `title:` frontmatter, `description:` frontmatter, H1, H2s, word count, link count. Store as baseline for the report.
+
+Identify recently changed files: `git log --oneline -2 --name-only -- docs/ README.md`
+
+## Phase 2: Meta Tags
+
+For each file with YAML frontmatter:
+
+**Title** (`title:` field):
+- Must be 50-60 characters
+- Must contain a primary keyword
+- Must be unique across all pages
+- Auto-fix generic titles using domain context
+
+**Description** (`description:` field):
+- Must be 120-160 characters
+- Must contain primary keyword
+- Must be unique — no duplicates
+- Auto-fix from SKILL.md frontmatter or first paragraph
+
+Run SEO checker on built HTML pages:
+```bash
+python3 marketing-skill/seo-audit/scripts/seo_checker.py --file site/{path}/index.html
+```
+
+## Phase 3: Content Quality
+
+**Heading structure:** One H1 per page, no skipped levels, keywords in headings.
+
+**Readability:** Run content scorer:
+```bash
+python3 marketing-skill/content-production/scripts/content_scorer.py {file}
+```
+Target: readability ≥ 70, structure ≥ 60.
+
+**AI detection** (on non-generated files only):
+```bash
+python3 marketing-skill/content-humanizer/scripts/humanizer_scorer.py {file}
+```
+Flag pages < 50. Fix AI clichés: "delve", "leverage", "it's important to note", "comprehensive".
+
+**Do NOT rewrite** pages ranking well — only fix critical issues on those.
+
+## Phase 4: Keywords
+
+Check each page has its primary keyword in: title, description, H1, first paragraph, at least one H2.
+
+Keyword density: 1-2% for primary. Flag and reduce if > 3%.
+
+**Never change existing URLs.** Only optimize content and meta tags.
+
+## Phase 5: Links
+
+**Internal links:** Verify all `[text](url)` targets exist. Fix broken links.
+
+**Duplicate content:**
+```bash
+grep -rh '^description:' docs/**/*.md | sort | uniq -d
+```
+Make each duplicate unique.
+
+**Orphan pages:** Find pages not in `mkdocs.yml` nav. Add them.
+
+## Phase 6: Sitemap
+
+Rebuild the site to regenerate sitemap:
+```bash
+mkdocs build
+```
+
+Analyze the sitemap:
+```bash
+python3 marketing-skill/site-architecture/scripts/sitemap_analyzer.py site/sitemap.xml
+```
+
+Verify all pages appear, no duplicates, no broken URLs.
+
+## Phase 7: Report
+
+Present a summary showing: pages scanned, issues found, auto-fixes applied, manual review items, broken links fixed, orphans resolved, sitemap URL count. List preserved pages that were not modified.