EPIC: Documentation Architecture, Contributor Onboarding & Quality Governance

## Overview

This sub-EPIC provides a first-class onboarding and documentation experience for both developers and production operators, along with automated AI-assisted development governance.

## Goals

1. **Contributor Experience**: Purify `CONTRIBUTING.md` with accurate toolchain guidance and clear architectural boundaries.
2. **README Refresh**: Streamline `README.md` into a 60-second quickstart, delegating detailed operator and deployment guides to dedicated files.
3. **Asset Organization**: Move static diagram assets out of root into `docs/assets/`.
4. **Documentation Platform**: Build and publish a cohesive Rust-book-style documentation site
5. **Quality Gates**: Establish automated AI-assisted development governance and quality checks