Dragging a piece
Highlight the cells, then place the piece.
While the player drags a piece, BlockPuzzleDragComponent moves its image. It converts the pointer position to board coordinates and calls previewPlacement to highlight cells. Releasing the piece sends PlacementRequested, and canceling the gesture clears the highlight. BlockPuzzleDragComponent.ts
Pick up a pieceRemember the selected piece
DragHighlight the cells underneath
ReleaseRequest the move
To forward drag input to an FSM in another game, attach DragInputBridgeComponent. Set eventType in its configuration. The component sends that event with coordinates when the drag starts, moves, and ends.