Sonnet worker for /ultra-skill-author-local. Consumes concept-extractor JSON
plus source file, writes a 150-600 word draft to .drafts/<slug>.md with the
9-field frontmatter contract (review_status=pending, ngram_overlap_score=null).
Imperative voice, progressive disclosure, no verbatim copy from source.
Aborts with too-technical-to-paraphrase if the subject can't be rephrased.
Plan: .claude/projects/2026-04-18-skill-factory-fase-1-mvp/plan.md (step 7)
