Fix waypoint drag, host election, segment routing, debug panel

Waypoint drag:
- Use observeDeep instead of observe to detect Y.Map property changes

Host election:
- Extracted to host-election.ts with 8 unit tests
- Simple rule: lowest real client ID is always host, deterministic
- Always sets role (host or participant), no missing roles
- Filters server docs (empty awareness state) from election

BRouter routing:
- Route segment-by-segment like bikerouter.de (one request per
  waypoint pair), guarantees route passes through every waypoint
- Merge GeoJSON segments with accumulated stats
- 8 unit tests for segment merging and waypoint splitting

Awareness cleanup:
- Track client IDs per WebSocket connection
- Immediately remove awareness on WebSocket close

Debug panel:
- Visibility + expanded state persisted in localStorage
- Hotkey (Shift+Cmd+Option+T) toggles visibility
- Labels server docs as (server)
- All logic self-contained in YjsDebugPanel.tsx

User identity:
- Color and name persisted in localStorage across reloads

Tests: 32 total (16 existing + 8 host election + 8 routing)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/app/components/PlannerMap.tsx

@@ -127,11 +127,11 @@ export function PlannerMap({ yjs, onRouteRequest, highlightPosition }: PlannerMa
       }
     };
 
-    yjs.waypoints.observe(update);
+    yjs.waypoints.observeDeep(update);
     update();
 
     return () => {
-      yjs.waypoints.unobserve(update);
+      yjs.waypoints.unobserveDeep(update);
     };
   }, [yjs.waypoints, onRouteRequest]);