Replace manual pointer event handling with the framework's
dragDropEventEffect utility. Update DragController to manage
DisposableBag for cleanup and pass containers instead of
pointers to drag callbacks. Add framework path alias to
tsconfig and fix loop variable shadowing in LostItemManager.
Move magic numbers and style constants to src/config.ts.
Decompose InventoryWidget into DragController, ItemRenderer,
and LostItemManager for better separation of concerns. Add
createButton utility and remove unused CombatUnitWidget.
Update scenes to import from centralized config.
hypercross