fix(wayland): route keys by keyboard focus, not pointer focus

keyboard_enter and keyboard_leave were empty and keyboard_key dereferenced
Device::focusedWindow, which only a pointer-enter sets: the first key
event in a window the pointer never entered — every key on a touch phone,
or a key typed while the pointer hovers another window — dereferenced a
null pointer, and keys typed after the pointer left went nowhere.

Keyboard focus is its own thing in Wayland. wl_keyboard.enter now resolves
its surface to the Window into Device::keyboardWindow, leave clears it
together with the held keys (their releases happen elsewhere) and stops
the repeat, and keyboard_key and TickKeyRepeats deliver to that window and
drop a key that has none.

interfaces/Crafter.Graphics-Device.cppm

@@ -49,6 +49,11 @@ export namespace Crafter {
         inline static xkb_keymap* xkb_keymap;
         inline static wl_compositor* compositor = nullptr;
         inline static Window* focusedWindow = nullptr;
+        // The window with keyboard focus (wl_keyboard.enter/leave), apart from
+        // the pointer's: a key arrives without the pointer ever having entered
+        // (a touch phone, a key typed while the pointer hovers elsewhere), so the
+        // keyboard handlers route by this and never by focusedWindow.
+        inline static Window* keyboardWindow = nullptr;
         inline static wl_shm* shm = nullptr;
         inline static wp_viewporter* wpViewporter = nullptr;
         inline static xkb_context* xkb_context = xkb_context_new(XKB_CONTEXT_NO_FLAGS);