ADD: IBL engine side

src/core/ibl_manager.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <core/vk_types.h>
+#include <string>
+
+class EngineContext;
+
+struct IBLPaths
+{
+    std::string specularCube; // .ktx2 (GPU-ready BC6H or R16G16B16A16)
+    std::string diffuseCube;  // .ktx2
+    std::string brdfLut2D;    // .ktx2 (BC5 RG UNORM or similar)
+};
+
+// Minimal IBL asset owner with optional residency control.
+class IBLManager
+{
+public:
+    void init(EngineContext* ctx) { _ctx = ctx; }
+
+    // Load all three textures. Returns true when specular+diffuse (and optional LUT) are resident.
+    bool load(const IBLPaths& paths);
+
+    // Release GPU memory and patch to fallbacks handled by the caller.
+    void unload();
+
+    bool resident() const { return _spec.image != VK_NULL_HANDLE || _diff.image != VK_NULL_HANDLE; }
+
+    AllocatedImage specular() const { return _spec; }
+    AllocatedImage diffuse()  const { return _diff; }
+    AllocatedImage brdf()     const { return _brdf; }
+
+private:
+    EngineContext* _ctx{nullptr};
+    AllocatedImage _spec{};
+    AllocatedImage _diff{};
+    AllocatedImage _brdf{};
+};
+