Summary

• Add Compare Flows option to the File menu that opens a .drawd file picker and diffs the selected file against the current canvas
• New diffFlows() utility compares all entity types (screens, connections, hotspots, documents, data models, sticky notes, screen groups) by ID with field-level change tracking
• Uses fingerprinting for large fields (imageData, svgContent) to avoid multi-MB string comparisons
• New FlowDiffModal displays a color-coded summary (green/red/yellow) with collapsible categories and expandable per-field change details

Test plan

• 16 unit tests for diffFlows covering identical flows, added/removed/modified entities, image fingerprinting, hotspot sub-diffs, metadata exclusions, and summary count consistency
• Manual: open editor with a flow, File > Compare Flows, select a different .drawd file -- verify diff modal shows correct categorized changes
• Manual: compare identical file -- verify "No differences found" message
• Manual: cancel file picker -- verify no error or modal appears
• Lint passes
• Build succeeds