feat: stabilize test suite and add UIDrawable methods

- Add visible, opacity properties to all UI classes (#87, #88)
- Add get_bounds(), move(), resize() methods to UIDrawable (#89, #98)
- Create UIDrawable_methods.h with template implementations
- Fix test termination issues - all tests now exit properly
- Fix test_sprite_texture_swap.py click handler signature
- Fix test_drawable_base.py segfault in headless mode
- Convert audio objects to pointers for cleanup (OpenAL warning persists)
- Remove debug print statements from UICaption
- Special handling for UIEntity to delegate drawable methods to sprite

All test files are now "airtight" - they complete successfully,
terminate on their own, and handle edge cases properly.

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

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

src/UIGrid.h

@@ -123,6 +123,9 @@ public:
     
 };
 
+// Forward declaration of methods array
+extern PyMethodDef UIGrid_all_methods[];
+
 namespace mcrfpydef {
     static PyTypeObject PyUIGridType = {
         .ob_base = {.ob_base = {.ob_refcnt = 1, .ob_type = NULL}, .ob_size = 0},
@@ -142,7 +145,7 @@ namespace mcrfpydef {
         //.tp_iternext
         .tp_flags = Py_TPFLAGS_DEFAULT,
         .tp_doc = PyDoc_STR("docstring"),
-        .tp_methods = UIGrid::methods,
+        .tp_methods = UIGrid_all_methods,
         //.tp_members = UIGrid::members,
         .tp_getset = UIGrid::getsetters,
         //.tp_base = NULL,