[Feat] (Diligent, MG_Impl): wire GenerateMipmap via Diligent GPU mip generation

- Create state textures with MISC_TEXTURE_FLAG_GENERATE_MIPS
- GenerateMipmap resolves active GL_TEXTURE_2D and calls IDeviceContext::GenerateMips
- Update handoff; 16 Diligent tests pass

HANDOFF_DILIGENT.md

@@ -158,6 +158,7 @@ Verified locally on Turnip Adreno 750:
   - `BlitFramebuffer` (same-size color copy between current read/draw FBOs)
   - `CopyTexImage2D` / `CopyTexSubImage2D` (whole-color copy fallback)
   - `CopyImageSubData` (whole-texture copy between two texture objects)
+  - `GenerateMipmap` (Diligent GPU mip generation on state textures)
   - `GetTexImage` / `GetTextureImage` (RGBA8 readback)
   - `ReadPixels` from default and user color attachments
 - Primitive expansion:
@@ -218,7 +219,7 @@ Notes:
 - Global UBO (default-block `glUniform*`) and named application UBO blocks (through `glBindBufferBase`/`glUniformBlockBinding`) now upload and bind; SSBOs are still not fed from frontend buffer bindings.
 - No swapchain / EGL window surface presentation yet; `Present()` only flushes.
 - No transform feedback / queries / sync / readback of non-color resources.
-- Draw range, multi-draw, instanced-draw wrappers, clear-buffer, blit, read-pixels, CopyTexImage*, GetTexImage/GetTextureImage and indirect draws are now wired; buffer subdata paths still remain.
+- Draw range, multi-draw, instanced-draw wrappers, clear-buffer, blit, read-pixels, CopyTexImage*, CopyImageSubData, GenerateMipmap, GetTexImage/GetTextureImage and indirect draws are now wired; buffer subdata paths still remain.
 - A last-PSO cache now avoids recreating the pipeline when program/render-state/topology/VAO layout is unchanged; texture/UBO resources are still rebound dynamically per draw.
 - The `GLFunctionsTable` is only partially populated.
 

MobileGL/MG_Backend/Diligent/BackendObject_Diligent.cpp

@@ -539,6 +539,18 @@ namespace MobileGL::MG_Backend::DiligentBackend {
             }
         }
 
+        void GenerateMipmap(GLenum target) {
+            auto* renderer = GetActiveRenderer();
+            if (renderer == nullptr || MG_State::pGLContext == nullptr || target != GL_TEXTURE_2D) {
+                return;
+            }
+            auto& unit = MG_State::pGLContext->GetTextureUnitObject(MG_State::pGLContext->GetActiveTextureUnit());
+            auto texture = unit.GetBindingSlot(TextureTarget::Texture2D).GetBoundObject();
+            if (texture) {
+                renderer->GenerateMipmap(*texture);
+            }
+        }
+
         void Present() {
             auto* renderer = GetActiveRenderer();
             if (renderer != nullptr) {
@@ -653,6 +665,7 @@ namespace MobileGL::MG_Backend::DiligentBackend {
         m_functions.GL.CopyTexImage2D = CopyTexImage2D;
         m_functions.GL.CopyTexSubImage2D = CopyTexSubImage2D;
         m_functions.GL.CopyImageSubData = CopyImageSubData;
+        m_functions.GL.GenerateMipmap = GenerateMipmap;
         m_functions.GL.GetTexImage = GetTexImage;
         m_functions.GL.GetTextureImage = GetTextureImage;
         m_functions.GL.ReadPixels = ReadPixels;

MobileGL/MG_Backend/Diligent/Renderer/DiligentRenderer.cpp

@@ -714,6 +714,7 @@ void main()
             } else {
                 texDesc.BindFlags |= ::Diligent::BIND_RENDER_TARGET;
             }
+            texDesc.MiscFlags = ::Diligent::MISC_TEXTURE_FLAG_GENERATE_MIPS;
 
             ::Diligent::RefCntAutoPtr<::Diligent::ITexture> pTexture;
             m_pDevice->CreateTexture(texDesc, nullptr, &pTexture);
@@ -1839,6 +1840,17 @@ void main()
         m_pContext->CopyTexture(copyAttribs);
     }
 
+    void DiligentRenderer::GenerateMipmap(MG_State::GLState::ITextureObject& texture) {
+        if (m_pContext == nullptr || SyncTexture(texture) == nullptr) {
+            return;
+        }
+        auto it = m_textureCache.find(texture.GetLifetimeId());
+        if (it == m_textureCache.end() || !it->second.SRV) {
+            return;
+        }
+        m_pContext->GenerateMips(it->second.SRV);
+    }
+
     Bool DiligentRenderer::ReadTextureImage(MG_State::GLState::ITextureObject& texture, Uint32 level,
                                          void* pixels) {
         if (!m_initialized || !m_pContext || pixels == nullptr) {

MobileGL/MG_Backend/Diligent/Renderer/DiligentRenderer.h

@@ -67,6 +67,7 @@ namespace MobileGL::MG_Backend::DiligentBackend {
                              GLbitfield mask, GLenum filter);
         void CopyReadFramebufferToTexture(MG_State::GLState::ITextureObject& dst);
         void CopyTextureSubData(MG_State::GLState::ITextureObject& src, MG_State::GLState::ITextureObject& dst);
+        void GenerateMipmap(MG_State::GLState::ITextureObject& texture);
         Bool ReadTextureImage(MG_State::GLState::ITextureObject& texture, Uint32 level, void* pixels);
         void Present();