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/UIEntity.h

@@ -68,6 +68,9 @@ public:
     static PyObject* repr(PyUIEntityObject* self);
 };
 
+// Forward declaration of methods array
+extern PyMethodDef UIEntity_all_methods[];
+
 namespace mcrfpydef {
     static PyTypeObject PyUIEntityType = {
         .ob_base = {.ob_base = {.ob_refcnt = 1, .ob_type = NULL}, .ob_size = 0},
@@ -77,7 +80,7 @@ namespace mcrfpydef {
         .tp_repr = (reprfunc)UIEntity::repr,
         .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
         .tp_doc = "UIEntity objects",
-        .tp_methods = UIEntity::methods,
+        .tp_methods = UIEntity_all_methods,
         .tp_getset = UIEntity::getsetters,
         .tp_init = (initproc)UIEntity::init,
         .tp_new = PyType_GenericNew,