Adds local development tools for rapid plugin iteration without deploying to RPi:
- VisualTestDisplayManager: renders real pixels via PIL (same fonts/interface as production)
- Dev preview server (Flask): interactive web UI with plugin picker, auto-generated config
forms, zoom/grid controls, and mock data support for API-dependent plugins
- CLI render script: render any plugin to PNG for AI-assisted visual feedback loops
- Updated test runner and conftest to auto-detect plugin-repos/ directory
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
