Material list volume doesn't update after deleting items

Entries in a material list can be deleted within the editor of their respective activity. Doing so will remove them from the material overview as well as from their specific list.
However, the amount of items within that list is not updated on the side view, meaning that a material list with 5 entries will keep displaying the amount 5 even after 2 entries have been deleted. If this list is viewed, those two entries are removed, but the side view doesn't update until a refresh of the whole site.

https://github.com/user-attachments/assets/e54395f7-bf1c-42b3-b012-08bc0d51f5e7

Reproduce the deletion flow from the material list editor and observe the material overview's side view before and after removing entries. Trace how the list count is refreshed when the list is viewed, then ensure the side view reflects deletions without a full-site refresh. Done when the displayed count matches the remaining entries immediately after deletion.

Written by the indexing model from the issue text.