Fix taskbar on main branch

On kwin, multiple apps that run through the proxy all show up in taskbar as if they are windows from the same applications. Figure out why and potentially fix this problem.

Reproduce the taskbar behavior on the main branch with multiple applications running through the proxy, then trace how their window identity is presented to KWin. Done means proxied applications appear as distinct taskbar entries rather than being grouped as windows from one application.

Written by the indexing model from the issue text.