[Feat] (Diligent): wire SetSwapInterval no-op

- GlobalBackendFunctionsTable.SetSwapInterval is now present; offscreen renderer ignores it
- Update handoff; 16 Diligent tests pass

HANDOFF_DILIGENT.md

@@ -219,7 +219,7 @@ Notes:
 - User framebuffers now support texture color attachments, renderbuffer color readback, multiple simultaneous color targets, and depth/stencil texture or renderbuffer attachments.
 - Textures auto-sync `ITextureObject` → Diligent resources, including mip levels and sampler state; compressed textures and integer/3-channel formats that Diligent lacks are still skipped.
 - 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 swapchain / EGL window surface presentation yet; `Present()` only flushes and `SetSwapInterval` is a no-op.
 - No transform feedback / GPU-accelerated queries / non-color readback; fence sync and timer queries use CPU fallbacks.
 - 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.

MobileGL/MG_Backend/Diligent/BackendObject_Diligent.cpp

@@ -658,6 +658,11 @@ namespace MobileGL::MG_Backend::DiligentBackend {
             return true;
         }
 
+        void SetSwapInterval(Int interval) {
+            // No native swapchain yet; the offscreen renderer ignores the interval.
+            (void)interval;
+        }
+
         void Present() {
             auto* renderer = GetActiveRenderer();
             if (renderer != nullptr) {
@@ -790,6 +795,7 @@ namespace MobileGL::MG_Backend::DiligentBackend {
         m_functions.GL.GetQueryResult64 = GetQueryResult64;
         m_functions.GL.DeleteBackendQuery = DeleteBackendQuery;
         m_functions.Present = Present;
+        m_functions.SetSwapInterval = SetSwapInterval;
 
         m_initialized = true;
     }