Implement Planner map UI with collaborative editing (Groups 5+6)
Core Planner experience:
- Full-screen Leaflet map with OSM/OpenTopoMap/CyclOSM layers
- Click to add waypoints, drag to move, right-click to delete
- Waypoint sidebar with reorder, delete, route stats
- Real-time Yjs sync between participants
- Live cursors showing other users' mouse positions on the map
Routing:
- Host election via Yjs awareness (lowest client ID)
- Auto-failover when host disconnects
- Debounced BRouter route computation (500ms)
- Route polyline display from BRouter GeoJSON
- Route stats (distance, elevation gain/loss)
Client-side architecture:
- useYjs hook: WebSocket connection, awareness, document management
- useRouting hook: host election, route computation, stats parsing
- PlannerMap component: Leaflet + Yjs integration
- WaypointSidebar component: list with reorder/delete
- Lazy-loaded components for code splitting
Remaining: elevation chart, profile selector, GPX export (tasks 6.7-6.9)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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