[client] ds: separate grab and capture logic

Currently, (un)grabPointer is used both for tracking/confining the mouse
in normal mode, as well as entering/exiting capture mode. This makes it
impossible to use separate cursor logic for capture mode, which is needed
to deal with overlapping windows for the Wayland backend.

This commit creates separate (un)capturePointer for entering/exiting
capture mode. There should be no behaviour changes.

client/src/app.c

@@ -46,6 +46,16 @@ bool app_isCaptureMode(void)
   return g_cursor.grab;
 }
 
+bool app_isCaptureOnlyMode(void)
+{
+  return g_params.captureInputOnly;
+}
+
+bool app_isFormatValid(void)
+{
+  return g_state.formatValid;
+}
+
 void app_updateCursorPos(double x, double y)
 {
   g_cursor.pos.x = x;