Migrate from SDL2 to SDL3
- Replace sdlpp with a custom SDL3 C++ wrapper in sdl3.hpp.
- Update Makefile and dependencies to use SDL3.
- Refactor Render and Deferred classes to use glm::ivec2 for screen size.
- Update event handling in SceneEditor and Gameplay for SDL3 API changes.
- Transition audio handling to SDL3’s new audio stream API.
- Introduce GameMode to distinguish between game and editor modes.
No stream today, not feeling well.