[jaygeorge]

Depends on #15676.

Description of the Problem

You can drag assets deeper into subfolders, but there's no way to drag one back up. To move an asset into a parent folder, or back to the top, you have to use the Move action instead.

What this PR Does

The breadcrumbs above the asset browser are now drop targets, so you can drag an asset or folder onto any parent folder, including "All".

• The breadcrumb you're over gets the same blue ring as a folder in grid view. In list view, folders now get the ring around their icon and name too, instead of the faint row background.
• While a move is running, the items show a spinner and can't be clicked. Then a "Moved to …" toast appears and the listing refreshes.
• Only items you're allowed to move light up a drop target. A folder can't be dropped onto itself, and anything already in the destination is skipped.
• While searching, results can come from anywhere, so the current folder's breadcrumb accepts drops too.

The move itself lives in Browser rather than in the grid and list components, so it carries on correctly if you switch views mid-move. Each move's spinners stay until the refreshed listing comes back, and the selection is updated in that same render. Moved assets get new IDs, so the action's own replaceInSelections callback keeps them selected rather than them silently dropping out (which matters in the asset picker, where the selection is what you're picking).

drag-to-breadcrumbs.mp4

How to Reproduce

1. Go to Assets and open a folder at least two levels deep.
2. Drag an asset onto "All" or a parent folder in the breadcrumbs.
3. It moves there.