kded6's detectPlatform() forces QT_QPA_PLATFORM=wayland regardless
of external environment. On Redox, Qt6 Wayland QPA crashes during
wl_registry init (page fault at null+8). kded6 is a headless
D-Bus daemon — it does not need Wayland.
Added #ifdef Q_OS_REDOX guard: use 'offscreen' instead of 'wayland'.
Combined with libwayland null guards, this provides defense in depth
against the Qt6 Wayland crash on Redox.
vasilito
652af71a9c