Add diagram editor with Mermaid import and image support

[JE-Chen]

Summary

• Add a full-featured WYSIWYG architecture diagram editor under Tools > Diagram Editor
• Support Mermaid flowchart syntax import with automatic BFS-based layout
• Support local file and URL image embedding on the canvas
• Add CLAUDE.md project documentation

Features

Diagram Editor Core

• Node shapes: Rectangle, Rounded Rect, Ellipse, Diamond
• Connections: edge-to-edge cubic bezier with arrowhead, solid/dashed/dotted styles
• Resize handles on all nodes and images (4-corner drag)
• Undo/Redo via snapshot-based QUndoStack (Ctrl+Z / Ctrl+Y)
• Grid background with snap toggle
• Property panel for node (text, size, shape, colors, font), connection (label, style, color, width), and image (caption, source, size)
• Align tools: left / right / top / bottom / center H/V / distribute H/V
• Copy/Paste/Duplicate, right-click context menu
• Keyboard shortcuts: Ctrl+Z/Y/C/V/D/S/A, Delete, Escape
• Export: PNG (2x retina) and SVG
• Save/Load: .diagram.json format
• Tab + Dock support

Mermaid Import

• Paste Mermaid graph TD/LR/RL/BT syntax and auto-generate diagram
• Bracket-to-shape mapping: [] rect, () rounded, {} diamond, (()) ellipse
• Arrow styles: --> solid, -.-> dashed, ==> thick
• Label support: -->|label| and -- label -->
• Chained edges: A --> B --> C
• Auto BFS layered layout with text-adaptive node widths

Image Support

• Local images: PNG, JPG, BMP, GIF, SVG, WebP via file dialog
• URL images: paste any image URL, auto-downloaded
• Images are movable, resizable, with optional caption
• Image source paths saved in diagram JSON for reload

Performance

• BSP tree index (depth 14) for O(log n) spatial queries
• DeviceCoordinateCache on all shape bodies, connections, and images
• MinimalViewportUpdate — only repaint dirty regions
• CacheBackground — grid painted once, blitted on scroll

i18n

• ~70 new keys in both English and Traditional Chinese

Files changed

• New (pybreeze/pybreeze_ui/diagram_editor/): 8 files, ~3100 lines
• Modified: tools_menu.py, extend_english.py, extend_traditional_chinese.py
• New: CLAUDE.md

Test plan

• All 49 existing unit tests pass
• All module imports verified
• Manual: create nodes (all 4 shapes), connect them, resize, undo/redo
• Manual: import Mermaid code, verify layout
• Manual: add local image and URL image
• Manual: save diagram, close, reopen and verify
• Manual: export PNG and SVG

[codacy-production]

Not up to standards ⛔

🔴 Issues 1 high · 2 medium

Alerts:
⚠ 3 issues (≤ 0 issues of at least minor severity)

Results:
3 new issues

Category	Results
ErrorProne	1 high
Security	2 medium

View in Codacy

🟢 Metrics 545 complexity · 4 duplication

Metric	Results
Complexity	545
Duplication	4

View in Codacy

_{TIP This summary will be updated as you push new changes. Give us feedback}

[sonarqubecloud]

Quality Gate failed

Failed conditions
4 Security Hotspots

See analysis details on SonarQube Cloud