feat: add RAII window class with OpenGL 4.1 context

- Add cbt::window class in cbt/ directory with RAII lifecycle
- Add setup_opengl and info_opengl for glad init and GL info
- Add Q key to quit the application
- Update CMakeLists.txt with glfw3 and glad dependencies
- Update AGENTS.md with snake_case naming and shell conventions

cuber.cpp

@@ -1,26 +1,27 @@
-#include <chrono>
-#include <thread>
+#define GLFW_INCLUDE_NONE
+#include "GLFW/glfw3.h"
 
-#include "fmt/std.h"
+#include "cbt/window.hpp"
 
-auto main(int argc, char const* argv[]) -> int {
-    using namespace std::chrono;
-    using namespace std::literals;
+#include "glad/glad.h"
 
-    auto start = steady_clock::now();
+auto main(int, char const*[]) -> int {
+    auto w = cbt::window("cuber", 1280, 720);
 
-    while (true) {
-        auto elapsed = steady_clock::now() - start;
-        auto totalSec = duration_cast<seconds>(elapsed).count();
-        auto h = totalSec / 3600;
-        auto m = (totalSec % 3600) / 60;
-        auto s = totalSec % 60;
-        auto ms = duration_cast<milliseconds>(elapsed % 1s).count();
+    if (!w.valid()) {
+        return 1;
+    }
 
-        fmt::print("\033[32m{:02}:{:02}:{:02}\033[0m.\033[90m{:03}\033[0m\r",
-                   h, m, s, ms);
+    while (!w.should_close()) {
+        if (glfwGetKey(static_cast<GLFWwindow*>(w.raw()), GLFW_KEY_Q) == GLFW_PRESS) {
+            break;
+        }
 
-        std::this_thread::sleep_for(10ms);
+        glClearColor(0.6f, 0.8f, 1.0f, 1.0f);
+        glClear(GL_COLOR_BUFFER_BIT);
+
+        w.swap_buffers();
+        w.poll_events();
     }
 
     return 0;