Implemented foundational pane system using eframe/egui:
- Workspace structure with lightningbeam-core and lightningbeam-editor
- Layout data structures matching existing JSON schema
- All 8 predefined layouts (Animation, Video Editing, Audio/DAW, etc.)
- Recursive pane rendering with visual dividers
- Layout switcher menu
- Color-coded pane types for visualization
Foundation complete for interactive pane operations (resize, split, join).
Skyler Lehmkuhl