fix: encapsulate OpenGL types in VertexAttribute to eliminate raw GL API usage in tests

- Add VertexAttributeType and VertexAttributeNormalized enums in OpenGLVertexArray.h
- Add ToGLAttributeType() converter in OpenGLVertexArray.cpp
- Remove glActiveTexture() call from quad test (already handled by texture.Bind())
- Remove #include <glad/glad.h> from triangle test
- Update unit tests to use encapsulated enums

All three OpenGL integration tests (minimal, triangle, quad) pass with 0% pixel difference.

tests/RHI/OpenGL/integration/triangle/main.cpp

@@ -5,8 +5,6 @@
 
 #include <windows.h>
 
-#include <glad/glad.h>
-
 #include "XCEngine/RHI/OpenGL/OpenGLDevice.h"
 #include "XCEngine/RHI/OpenGL/OpenGLSwapChain.h"
 #include "XCEngine/RHI/OpenGL/OpenGLCommandList.h"
@@ -124,8 +122,8 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
     VertexAttribute posAttr = {};
     posAttr.index = 0;
     posAttr.count = 4;
-    posAttr.type = GL_FLOAT;
-    posAttr.normalized = GL_FALSE;
+    posAttr.type = VertexAttributeType::Float;
+    posAttr.normalized = VertexAttributeNormalized::False;
     posAttr.stride = sizeof(Vertex);
     posAttr.offset = 0;
     vertexArray.AddVertexBuffer(vertexBuffer.GetID(), posAttr);
@@ -133,8 +131,8 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
     VertexAttribute colAttr = {};
     colAttr.index = 1;
     colAttr.count = 4;
-    colAttr.type = GL_FLOAT;
-    colAttr.normalized = GL_FALSE;
+    colAttr.type = VertexAttributeType::Float;
+    colAttr.normalized = VertexAttributeNormalized::False;
     colAttr.stride = sizeof(Vertex);
     colAttr.offset = sizeof(float) * 4;
     vertexArray.AddVertexBuffer(vertexBuffer.GetID(), colAttr);