Implement history store with undo/redo stacks using structuredClone
snapshots. Add keyboard shortcuts for common operations (copy, paste,
delete, group, save, export). Implement save-as dialog (.pen file
download) and export dialog (PNG/SVG with scale options).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Set up the Fabric.js v7 canvas integration with bidirectional sync
to a Zustand document store. Includes drawing tools (select, rectangle,
ellipse, line, text, frame, hand), viewport pan/zoom, smart guides,
dimension labels, and the main editor layout with toolbar and status bar.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
