qmllint shipped with Qt 6.12 segfaults on the inline component
definition inside RunningAppsPanel.qml, breaking the
suse_tumbleweed_qt612 KDE Invent CI job. Move PanelIconButton out
to a sibling RunningAppsPanelButton.qml so qmllint never has to
parse a UiInlineComponent here.
The extracted file inlines its own colour-mix helper to keep it
self-contained and avoid leaking RunningAppsPanel internals.
Show running windows in the app drawer with previews, window
actions, and virtual desktop controls. Hide dock task icons while
the panel is open so the same windows are not duplicated.
Use TaskManager to move windows between desktops, and expose
desktop activation through the containment.
