bugfix: segfault in Grid.at() due to internal types not exported to module

After #184/#189 made GridPoint and GridPointState internal-only types,
code using PyObject_GetAttrString(mcrf_module, "GridPoint") would get
NULL and crash when dereferencing.

Fixed by using the type directly via &mcrfpydef::PyUIGridPointType
instead of looking it up in the module.

Affected functions:
- UIGrid::py_at()
- UIGridPointState::get_point()
- UIEntity::at()
- UIGridPointState_to_PyObject()

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/UIGrid.cpp

@@ -1182,8 +1182,8 @@ PyObject* UIGrid::py_at(PyUIGridObject* self, PyObject* args, PyObject* kwds)
         return NULL;
     }
 
-    //PyUIGridPointObject* obj = (PyUIGridPointObject*)((&PyUIGridPointType)->tp_alloc(&PyUIGridPointType, 0));
-    auto type = (PyTypeObject*)PyObject_GetAttrString(McRFPy_API::mcrf_module, "GridPoint");
+    // Use the type directly since GridPoint is internal-only (not exported to module)
+    auto type = &mcrfpydef::PyUIGridPointType;
     auto obj = (PyUIGridPointObject*)type->tp_alloc(type, 0);
     //auto target = std::static_pointer_cast<UIEntity>(target);
     // #123 - Use at() method to route through chunks for large grids