* feat: add avatar metrics tracking feature (#110)
Add AvatarMetrics dataclass for tracking avatar state snapshots
- Add AvatarMetrics dataclass for recording monthly snapshots
- Add metrics_history field to Avatar with opt-in tracking
- Implement automatic monthly snapshot recording in Simulator
- Add backward compatibility support for existing save files
- Set default tracking limit to 1200 months (100 years)
- Add comprehensive tests with 100% coverage
- Move documentation to specs directory with simplified chinese
* fix: convert Traditional Chinese comments to Simplified Chinese
修正程式碼中的繁體中文註解為簡體中文，以符合專案規範。
Fix Traditional Chinese comments to Simplified Chinese in codebase.
* feat: add draggable sidebar resizer
- Add resizer handle between map and event panel
- Sidebar width adjustable from 300px to 50% screen width
- Default width remains 400px
- Auto-adjust on window resize
* fix: preserve map zoom when resizing sidebar
Only update viewport screen size without re-fitting the map
* fix: use window size for canvas to prevent map scaling on resize
- Canvas size now based on window instead of container
- Sidebar resize only clips the visible area, map stays same size
- Remove CSS stretch on canvas element
* docs: update sidebar-resizer spec with canvas fix
