Add terrain grid resize commit handler to ViewportCanvas and App

src/app/App.tsx

@@ -16505,6 +16505,7 @@ export function App({
                   onSetPanelViewMode={handleSetViewportPanelViewMode}
                   onSetPanelDisplayMode={handleSetViewportPanelDisplayMode}
                   onTerrainBrushCommit={handleCommitTerrainBrushStroke}
+                  onTerrainGridResizeCommit={handleTerrainGridResizeCommit}
                   onCommitCreation={handleCommitCreation}
                   onCameraStateChange={(cameraState) => {
                     const previousCameraState =

src/viewport-three/ViewportCanvas.tsx

@@ -75,7 +75,7 @@ interface ViewportCanvasProps {
   focusSelection: EditorSelection;
   onSelectionChange(selection: EditorSelection): void;
   onTerrainBrushCommit(commit: TerrainBrushStrokeCommit): boolean;
-  onTerrainGridResizeCommit(terrain: Terrain): boolean;
+  onTerrainGridResizeCommit?(terrain: Terrain): boolean;
   onCommitCreation(toolPreview: CreationViewportToolPreview): boolean;
   onCameraStateChange(cameraState: ViewportPanelCameraState): void;
   onToolPreviewChange(toolPreview: ViewportToolPreview): void;
@@ -295,7 +295,7 @@ export function ViewportCanvas({
   focusSelection,
   onSelectionChange,
   onTerrainBrushCommit,
-  onTerrainGridResizeCommit,
+  onTerrainGridResizeCommit = () => false,
   onCommitCreation,
   onCameraStateChange,
   onToolPreviewChange,