feat: add OpenGL abstraction layer with RAII resources

- Replace window class with cbt::opengl::context
- Add buffer resource (VBO, EBO, UBO, SSBO) with move semantics
- Add texture resource with format/type enums and filtering
- Add descriptor_set for Vulkan-style resource binding
- All resources use RAII with proper cleanup

cuber.cpp

@@ -1,7 +1,7 @@
 #define GLFW_INCLUDE_NONE
 #include "GLFW/glfw3.h"
 
-#include "cbt/window.hpp"
+#include "cbt/opengl/context.hpp"
 
 #include <csignal>
 
@@ -10,9 +10,9 @@
 #include "glad/glad.h"
 
 auto main(int, char const*[]) -> int {
-    auto w = cbt::window("cuber", 1280, 720);
+    auto ctx = cbt::opengl::context("cuber", 1280, 720);
 
-    if (!w.valid()) {
+    if (!ctx.valid()) {
         return 1;
     }
 
@@ -29,18 +29,18 @@ auto main(int, char const*[]) -> int {
         while (io.poll()) {}
     };
 
-    while (!w.should_close()) {
+    while (!ctx.should_close()) {
         process_signals();
 
-        if (quit || glfwGetKey(static_cast<GLFWwindow*>(w.raw()), GLFW_KEY_Q) == GLFW_PRESS) {
+        if (quit || glfwGetKey(ctx.raw(), GLFW_KEY_Q) == GLFW_PRESS) {
             break;
         }
 
         glClearColor(0.6f, 0.8f, 1.0f, 1.0f);
         glClear(GL_COLOR_BUFFER_BIT);
 
-        w.swap_buffers();
-        w.poll_events();
+        ctx.swap_buffers();
+        ctx.poll_events();
     }
 
     return 0;