Adds interactive drag-and-drop functionality to the inventory spawner,
allowing users to move items within the grid.
- Implements `InventoryItemSpawnerCallbacks` to handle item movement
- Adds `moveItem` utility to update inventory state via signals
- Integrates `dragDropEventEffect` for item interaction
- Updates `InventoryTestScene` to demonstrate movement
- Adjusts text colors in `GRID_CONFIG` for better visibility
Implement `InventoryTestScene` to demonstrate reactive inventory
management using signals. Includes a grid-based visualization of items
and controls to add or remove items dynamically.
hypercross