chore: import upstream snapshot with attribution

engineering/skills/documentation/SKILL.md

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+---
+name: documentation
+description: Write and maintain technical documentation. Trigger with "write docs for", "document this", "create a README", "write a runbook", "onboarding guide", or when the user needs help with any form of technical writing — API docs, architecture docs, or operational runbooks.
+---
+
+# Technical Documentation
+
+Write clear, maintainable technical documentation for different audiences and purposes.
+
+## Document Types
+
+### README
+- What this is and why it exists
+- Quick start (< 5 minutes to first success)
+- Configuration and usage
+- Contributing guide
+
+### API Documentation
+- Endpoint reference with request/response examples
+- Authentication and error codes
+- Rate limits and pagination
+- SDK examples
+
+### Runbook
+- When to use this runbook
+- Prerequisites and access needed
+- Step-by-step procedure
+- Rollback steps
+- Escalation path
+
+### Architecture Doc
+- Context and goals
+- High-level design with diagrams
+- Key decisions and trade-offs
+- Data flow and integration points
+
+### Onboarding Guide
+- Environment setup
+- Key systems and how they connect
+- Common tasks with walkthroughs
+- Who to ask for what
+
+## Principles
+
+1. **Write for the reader** — Who is reading this and what do they need?
+2. **Start with the most useful information** — Don't bury the lede
+3. **Show, don't tell** — Code examples, commands, screenshots
+4. **Keep it current** — Outdated docs are worse than no docs
+5. **Link, don't duplicate** — Reference other docs instead of copying