feat(app): compile JSONC diagrams

[douglance]

Summary

• add termdraw compile for rendering JSONC diagram documents without opening the interactive editor
• support file/stdin input plus plain or fenced terminal-text output
• document the JSONC workflow and render a README architecture diagram through the new compiler

Details

The compiler maps a compact JSONC document into retained DrawState objects for boxes, lines, paint strokes, and text, then exports through the existing terminal-text rendering path. The app CLI keeps the existing interactive default behavior and routes the new compile subcommand separately.

Testing

• bun run check
• bun run build
• cd packages/app && bun run src/cli.tsx compile ../../docs/examples/architecture.diagram.jsonc

[benvinegar]

Was this to be able to save/restore diagrams? Is it covered by #19?