Add GSOpenGLBackend class for OpenGL integration

ps2xRuntime/include/runtime/gs/gs_opengl_backend.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "runtime/gs/gs_backend.h"
+#include <memory>
+
+class GSCpuBackend;
+
+// Fase de integración: comprueba que existe un contexto OpenGL ES 3.2
+// y conserva el comportamiento GS actual delegando las operaciones al backend CPU.
+// IMPORTANTE: todavía no rasteriza las primitivas GS en la GPU.
+class GSOpenGLBackend final : public GSRasterBackend
+{
+public:
+    GSOpenGLBackend();
+    ~GSOpenGLBackend() override;
+
+    bool IsOpenGLES32Available() const;
+    const char* GetOpenGLVersion() const;
+
+    void Initialize(uint8_t* vram, uint32_t vramSize) override;
+    void Reset() override;
+    void Submit(const GSPrimitiveBatch& batch) override;
+    void LoadClut(const GSTex0Reg& tex0, const GSTexClutReg& texclut) override;
+    void BeginTransfer(const GSTransferCommand& command) override;
+    void UploadImage(const uint8_t* data, uint32_t sizeBytes) override;
+    void Flush() override;
+    void TextureFlush() override;
+    void Sync(GSSyncReason reason) override;
+    PresentationFrame Present(const GSPresentationRequest& request) override;
+    bool ClearFramebuffer(const GSContext& context, uint32_t rgba) override;
+    uint32_t ConsumeLocalToHostBytes(uint8_t* dst, uint32_t maxBytes) override;
+    uint32_t ReadVram(uint32_t psm, uint32_t base, uint32_t bw,
+                      uint32_t x, uint32_t y) const override;
+    void WriteVram(uint32_t psm, uint32_t base, uint32_t bw,
+                   uint32_t x, uint32_t y, uint32_t value) override;
+    void SnapshotVram(std::vector<uint8_t>& out) const override;
+    GSTransferSnapshot GetTransferSnapshot() const override;
+
+private:
+    std::unique_ptr<GSCpuBackend> m_cpu;
+    bool m_gles32Available = false;
+    char m_glVersion[256]{};
+};