task(CAD-14): phase 3 - V2 select tool on v2 doc (click via bridge hitTest, shift-additive, box-select by center-in-bbox, onChange app channel via ref), bridge onChange wired

frontend/src/components/CanvasArea.tsx

@@ -46,6 +46,9 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
   /** CAD-14: Frische Prop-Referenz gegen Stale-Closure (Dispatcher/onChanged sind einmalig registriert). */
   const onElementCreatedRef = useRef(onElementCreated);
   onElementCreatedRef.current = onElementCreated;
+  /** CAD-14: Frische Prop-Referenz für Selection-Änderungen aus V2-Werkzeugen. */
+  const onSelectionChangeRef = useRef(onSelectionChange);
+  onSelectionChangeRef.current = onSelectionChange;
   const spatialIndexRef = useRef<SpatialIndex | null>(null);
   const layerManagerRef = useRef<LayerManager | null>(null);
   const selectionEngineRef = useRef<SelectionEngine | null>(null);
@@ -170,6 +173,9 @@ const CanvasArea: React.FC<CanvasAreaProps> = ({
           getIds: () => Array.from(selectionEngine.getSelectedIds()),
           setIds: (ids) => selectionEngine.selectByIds(ids, false),
           hitTest: (wx, wy, tol) => renderEngine.hitTest(wx, wy, tol),
+          // CAD-14: App-Kanal fuer V2-Werkzeuge (selectTool) — via Ref gegen
+          // Stale-Closure, derselbe Kanal wie die Legacy-Engine nutzt.
+          onChange: (ids) => onSelectionChangeRef.current?.(ids),
         }),
       });