docs: add starter kits documentation (plan §5.8)
All 8 starter kits are complete and ready for GitHub deployment:
- acb-starter-python (Python 3.13, stdlib only)
- acb-starter-go (Go 1.23, net/http)
- acb-starter-rust (Rust 1.83, axum)
- acb-starter-php (PHP 8.4, built-in server)
- acb-starter-typescript (TypeScript, Node.js http)
- acb-starter-javascript (JavaScript, Node.js http)
- acb-starter-java (Java 21, Javalin)
- acb-starter-csharp (C#, ASP.NET Core)
Each includes: HTTP server, HMAC verification, type definitions,
grid utilities (toroidal distance, BFS, neighbors), stub strategy,
Dockerfile, and README.
Kits are in ~/scratch/starter-kits/ pending GitHub repo creation.
Closes: bf-5e8v
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>