feat(ingest): downstream doc-coauthoring collaborative documentation workflow

[harshsinghmp]

Classification

actionable-feature

Context & Rationale

anthropics/skills/doc-coauthoring provides an official 3-stage co-authoring workflow (Context Gathering → Refinement & Structure → Reader Testing) that guides users through creating PRDs, RFCs, and decision docs.

Scope & Ingestion Plan

1. Ingest upstream from https://github.com/anthropics/skills/tree/main/skills/doc-coauthoring.
2. Place into skills/operations/doc-coauthoring.
3. Register in skills.manifest.json and catalog under Operations & Delivery.
4. Strip any proprietary connector dependencies to maintain vendor neutrality.

Verification Criteria

• skills/operations/doc-coauthoring/SKILL.md exists and passes manifest schema validation.
• Registered in skills.manifest.json.
• Validated via bun test.