Add Starlight documentation site with full content
Astro 5 + Starlight docs site with 17 pages covering all 30 mcserial
tools. Structured using Diataxis framework: tutorials, guides, reference,
and concepts. Includes Docker + caddy-docker-proxy deployment for
mcserial.l.zmesh.systems with HMR support behind reverse proxy.
Content pages:
- Landing page with feature overview and quick start
- Tutorials: getting started, loopback testing (loop://)
- Guides: RS-232 basics, RS-485/Modbus, file transfers, network ports
- Reference: common tools, RS-232 tools, RS-485 tools, file transfer
tools, URL schemes, MCP resources, environment variables
- Concepts: RS-232 vs RS-485, flow control