Add validation to keypressScene() for non-callable arguments

Added PyCallable_Check validation to ensure keypressScene() only
accepts callable objects. Now properly raises TypeError with a
clear error message when passed non-callable arguments like
strings, numbers, None, or dicts.

src/McRFPy_API.cpp

@@ -603,6 +603,13 @@ PyObject* McRFPy_API::_createScene(PyObject* self, PyObject* args) {
 PyObject* McRFPy_API::_keypressScene(PyObject* self, PyObject* args) {
     PyObject* callable;
 	if (!PyArg_ParseTuple(args, "O", &callable)) return NULL;
+    
+    // Validate that the argument is callable
+    if (!PyCallable_Check(callable)) {
+        PyErr_SetString(PyExc_TypeError, "keypressScene() argument must be callable");
+        return NULL;
+    }
+    
     /*
     if (game->currentScene()->key_callable != NULL and game->currentScene()->key_callable != Py_None)
     {
@@ -613,6 +620,7 @@ PyObject* McRFPy_API::_keypressScene(PyObject* self, PyObject* args) {
     Py_INCREF(Py_None);
     */
     game->currentScene()->key_callable = std::make_unique<PyKeyCallable>(callable);
+    Py_INCREF(Py_None);
     return Py_None;		
 }