feat(skills): import external marketing seo and obsidian skills

Import and normalize new skills from anthropics/skills, marketingskills, claude-seo, and obsidian-skills.

Align imported skills to repository validation rules, document provenance, and sync generated registry artifacts after the import.

docs/maintainers/skills-import-2026-03-21.md

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+# Skills Import - 2026-03-21
+
+This note records the skill import and normalization work completed on 2026-03-21.
+
+## Summary
+
+- Imported new skill directories from external repositories.
+- Normalized frontmatter for imported skills where needed.
+- Repaired imported dangling links that did not map cleanly into this repository.
+- Regenerated derived artifacts after import.
+
+## Imported Skills by Source
+
+### `anthropics/skills`
+
+- `claude-api`
+- `internal-comms`
+
+Note:
+- `docx`, `pdf`, `pptx`, and `xlsx` were not re-imported as separate directories because this repository already exposes those aliases as symlinks to `*-official` skill directories.
+
+### `coreyhaines31/marketingskills`
+
+- `ad-creative`
+- `ai-seo`
+- `churn-prevention`
+- `cold-email`
+- `content-strategy`
+- `lead-magnets`
+- `product-marketing-context`
+- `revops`
+- `sales-enablement`
+- `site-architecture`
+
+### `AgriciDaniel/claude-seo`
+
+- `seo`
+- `seo-competitor-pages`
+- `seo-content`
+- `seo-dataforseo`
+- `seo-geo`
+- `seo-hreflang`
+- `seo-image-gen`
+- `seo-images`
+- `seo-page`
+- `seo-plan`
+- `seo-programmatic`
+- `seo-schema`
+- `seo-sitemap`
+- `seo-technical`
+
+### `kepano/obsidian-skills`
+
+- `defuddle`
+- `json-canvas`
+- `obsidian-bases`
+- `obsidian-cli`
+- `obsidian-markdown`
+
+## Not Imported
+
+These repositories were analyzed earlier in the comparison work, but no new primary skills were imported from them in this batch:
+
+- `obra/superpowers`
+- `muratcankoylan/agent-skills-for-context-engineering`
+- `PleasePrompto/notebooklm-skill`
+
+## Validation
+
+Commands run during the import:
+
+```bash
+npm run validate
+npm run index
+npm run catalog
+```
+
+Result:
+
+- Validation passed after normalization.
+- Generated index count after import: `1304` skills.