fix graphical boot: DRM scheme detection, ConsoleKit bypass, boot chain deps

Three fixes for the KWin DRM device discovery failure:

1. drm_scheme_ready(): replace head -c 1 with exec 3< open test.
   Reading from a DRM scheme fd blocks because the scheme expects
   ioctl-style request/response, not streaming reads. Use open()
   success as the scheme availability probe instead.

2. ConsoleKitSession::create(): return nullptr immediately.
   The D-Bus isServiceRegistered() call can block indefinitely when
   the bus daemon doesn't fully implement org.freedesktop.DBus.
   With both LogindSession and ConsoleKitSession returning nullptr,
   Session::create() falls through to NoopSession which uses plain
   open() for DRM device access.

3. Boot chain deps: redox-drm depends on driver-manager,
   greeter depends on evdevd (keyboard/mouse ready before login).

Also includes: KF6 CMake build fixes, Qt6 platform patches,
libdrm Redox ioctl shim, and wayland.toml scheme check fix.

local/recipes/kde/kwin/source/src/tabletmodemanager.cpp

@@ -126,6 +126,8 @@
 #include <libudev.h>
 #include <libudev.h>
 #include <libudev.h>
+#include <libudev.h>
+#include <libudev.h>
 
 #include "backends/libinput/device.h"
 #include "core/inputdevice.h"