docs-rewrite

@nexus-substrate

Improve an existing technical doc in-place via a phased Audit → Research → Rewrite → Validate workflow. Calls docs-review for audit and validate; never re-derives scoring. Applies answer-first H2s, citation capsules, and info-gain markers per .rules/docs-rubric.md. Use when the user says "rewrite docs", "improve this doc", "optimize doc", "docs rewrite".