feat(viz): dp coin change

frontend/src/lib/visualizations/types.ts

@@ -86,6 +86,9 @@ export interface DataState {
   trees?: BinaryTreeState[];
   // Queue support
   queues?: QueueState[];
+  // Grid support (for DP visualizations)
+  grids?: GridState[];
+  gridPointers?: GridPointerState[];
 }
 
 /** Single step in the visualization */
@@ -246,3 +249,34 @@ export interface QueueState {
   elements: QueueElementState[];
   label?: string;
 }
+
+// ============================================
+// Grid Types (for DP visualizations)
+// ============================================
+
+/** State of a grid cell */
+export interface GridCellState {
+  id: string;
+  value: number | string;
+  row: number;
+  col: number;
+  state: 'normal' | 'highlighted' | 'comparing' | 'computing' | 'success' | 'dimmed';
+}
+
+/** Complete grid state */
+export interface GridState {
+  id: string;
+  cells: GridCellState[][]; // 2D array: cells[row][col]
+  colLabels?: (string | number)[];
+  rowLabels?: (string | number)[];
+  label?: string;
+}
+
+/** Pointer for grid visualization */
+export interface GridPointerState {
+  id: string;
+  name: string;
+  row: number;
+  col: number;
+  color: 'current' | 'dependency' | 'result' | 'default';
+}