[client] input: synchronize host lock state over LGMP

Cache native keyboard lock state across input-provider transitions and
reconcile it with HID LED feedback over LGMP.

Project raw and corrective lock-key transitions through the reliable
input FIFO, defer correction until outstanding transitions settle, and
recover from delayed or missing feedback without double toggling.

client/tests/mouse_test.c

@@ -288,6 +288,11 @@ void evdev_setGrab(bool keyboard, bool pointer)
   (void)pointer;
 }
 
+bool evdev_isExclusive(void)
+{
+  return false;
+}
+
 static bool inputSupports(void * opaque, LG_InputSupport support)
 {
   return support == LG_INPUT_SUPPORT_MOUSE_ABSOLUTE &&