Phase 4.2: Add GridView UIDrawable type (addresses #252)

GridView is a new UIDrawable that renders a GridData object independently.
Multiple GridViews can reference the same Grid for split-screen, minimap,
or different camera/zoom perspectives on shared grid state.

- New files: UIGridView.h/cpp with full rendering pipeline (copied from
  UIGrid::render, adapted to use grid_data pointer)
- Add UIGRIDVIEW to PyObjectsEnum
- Add UIGRIDVIEW cases to all switch(derived_type()) sites:
  Animation.cpp, UICollection.cpp, UIDrawable.cpp, McRFPy_API.cpp,
  ImGuiSceneExplorer.cpp
- Python type: mcrfpy.GridView(grid=, pos=, size=, zoom=, fill_color=)
- Properties: grid, center, zoom, fill_color, texture
- Register type with metaclass for callback support

All 258 existing tests pass. New GridView test suite added.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Animation.cpp

@@ -11,6 +11,7 @@
 #include "UICaption.h"
 #include "UISprite.h"
 #include "UIGrid.h"
+#include "UIGridView.h"
 #include "UILine.h"
 #include "UICircle.h"
 #include "UIArc.h"
@@ -557,6 +558,17 @@ static PyObject* convertDrawableToPython(std::shared_ptr<UIDrawable> drawable) {
             obj = (PyObject*)pyObj;
             break;
         }
+        case PyObjectsEnum::UIGRIDVIEW:
+        {
+            type = &mcrfpydef::PyUIGridViewType;
+            auto pyObj = (PyUIGridViewObject*)type->tp_alloc(type, 0);
+            if (pyObj) {
+                pyObj->data = std::static_pointer_cast<UIGridView>(drawable);
+                pyObj->weakreflist = NULL;
+            }
+            obj = (PyObject*)pyObj;
+            break;
+        }
         case PyObjectsEnum::UILINE:
         {
             type = &mcrfpydef::PyUILineType;