docs(planning): align ARCHITECTURE.md with project layout and patterns

- Update project name (opencode-cloud), CLI (occ), layout (core, cli-rust, cli-node, cli-node-*)
- Document Rust single source of truth, Node passthrough, Bollard-only Docker
- Add platform packages (optionalDependencies), config paths, service installation
- Revise patterns, anti-patterns, build order, distribution, and sources

Author: pRizz