Metal post-processing pipeline implementation

- Add custom Metal render target creation
- Implement post-processing without GPU-CPU-GPU copies
- Create Metal texture extraction system
- Add Metal CRT shader pipeline integration
- Modify screen rendering to use Metal when available
- Enable shaders by default for testing

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

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

source/external/jail_shader.h

@@ -4,6 +4,20 @@
 #include <string>  // Para basic_string, string
 
 namespace shader {
-bool init(SDL_Window *ventana, SDL_Texture *texturaBackBuffer, const std::string &vertexShader, const std::string &fragmentShader = "");
+bool init(SDL_Window *ventana, SDL_Texture *texturaBackBuffer, const std::string &shaderSource, const std::string &fragmentShader = "");
 void render();
+void cleanup();
+bool isUsingOpenGL();
+
+#ifdef __APPLE__
+namespace metal {
+bool initMetal(SDL_Window* window, SDL_Texture* backBuffer, const std::string& shaderFilename);
+SDL_Texture* createMetalRenderTarget(SDL_Renderer* renderer, int width, int height);
+void updateMetalTexture(SDL_Texture* backBuffer);
+void renderMetal();
+void renderWithPostProcessing(SDL_Renderer* renderer, SDL_Texture* sourceTexture);
+void cleanupMetal();
+}
+#endif
+
 }  // namespace shader