Document Aurelius-to-Nerva full-stack workflow

[PAMulligan]

Description

Create comprehensive documentation for the Aurelius → Nerva full-stack development workflow. The `/build-from-aurelius` pipeline is mentioned throughout the docs but lacks a dedicated walkthrough with concrete examples.

Why

The Aurelius-to-Nerva pipeline is one of Nerva's most unique value propositions — generating a matching backend from a frontend build spec. Without clear documentation and examples, this powerful feature is effectively invisible to potential users.

Acceptance Criteria

• Create `docs/schema-to-api/aurelius-pipeline.md` (currently referenced but does not exist)
• Document the full workflow:
  1. How Aurelius generates `build-spec.json`
  2. What data the Nerva pipeline extracts from it
  3. How the OpenAPI spec is generated from frontend needs
  4. How it feeds into `/build-from-schema`
  5. How the typed API client bridges both sides
• Include a concrete example with sample Aurelius `build-spec.json` input
• Show the generated OpenAPI spec output
• Document the `./scripts/generate-client.sh` typed client generation
• Add architecture diagram showing the Aurelius ↔ Nerva data flow
• Link from the main README and `docs/schema-to-api/README.md`
• CI passes