Inventory item visibility & scrolling according to width of item images

The engine shouldn't resize inventory items, it should be up to the adventure designer to set the size in json. Even in LZ the item image size varies - many are 90x90, which is unfortunately squeezed into 80x80 in inventoryAdd.

Right now the visible inventory size is set to seven items, and doesn't care about the actual width of the item images.

Therefore: calculate the room needed by each inventory item from the item image width.

Start by locating inventoryAdd and the JSON item-image size handling. Inspect how the current seven-item visible width is calculated, then verify that inventory space follows each image's width and that item images are no longer resized.

Written by the indexing model from the issue text.