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/ImGuiSceneExplorer.cpp

@@ -12,6 +12,7 @@
 #include "UICaption.h"
 #include "UISprite.h"
 #include "UIGrid.h"
+#include "UIGridView.h"
 #include "UIEntity.h"
 #include "ImGuiConsole.h"
 #include "PythonObjectCache.h"
@@ -285,6 +286,7 @@ const char* ImGuiSceneExplorer::getTypeName(UIDrawable* drawable) {
         case PyObjectsEnum::UICAPTION:    return "Caption";
         case PyObjectsEnum::UISPRITE:     return "Sprite";
         case PyObjectsEnum::UIGRID:       return "Grid";
+        case PyObjectsEnum::UIGRIDVIEW:   return "GridView";
         case PyObjectsEnum::UILINE:       return "Line";
         case PyObjectsEnum::UICIRCLE:     return "Circle";
         case PyObjectsEnum::UIARC:        return "Arc";