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/quad/main.cpp

@@ -127,8 +127,8 @@ 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);
@@ -136,8 +136,8 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
     VertexAttribute texAttr = {};
     texAttr.index = 1;
     texAttr.count = 2;
-    texAttr.type = GL_FLOAT;
-    texAttr.normalized = GL_FALSE;
+    texAttr.type = VertexAttributeType::Float;
+    texAttr.normalized = VertexAttributeNormalized::False;
     texAttr.stride = sizeof(Vertex);
     texAttr.offset = sizeof(float) * 4;
     vertexArray.AddVertexBuffer(vertexBuffer.GetID(), texAttr);
@@ -200,7 +200,6 @@ int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine
             pipelineState.Bind();
             vertexArray.Bind();
 
-            glActiveTexture(GL_TEXTURE0);
             texture.Bind(0);
             sampler.Bind(0);