[Fix] (DirectGLES): apply the read buffer when one FBO is bound as both draw and read

- SyncCurrentFBO skips the READ-target pass when the same GL FBO is bound as
  both draw and read (the common GL_FRAMEBUFFER case), but the read buffer
  (glReadBuffer) is only applied inside SyncToBackend's READ path — so the skip
  silently dropped every glReadBuffer change, leaving the backend read buffer
  stuck at COLOR_ATTACHMENT0.
- Extract the read-buffer application into BackendFramebufferObject::
  SyncReadBufferToBackend and invoke it from the skip branch (target == Read)
  as well as from SyncToBackend, so reads always target the right attachment.
- Bind the backend FBO as READ inside the helper before glReadBuffer, since the
  skip path only bound it as DRAW.
- Fixes KHR-GL3x.draw_buffers.draw_buffers_1 (reading COLOR_ATTACHMENT1 while
  the FBO stays GL_FRAMEBUFFER-bound returned attachment 0's value); the render
  was already correct, only the readback resolved the wrong attachment.

MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp

@@ -531,6 +531,18 @@ namespace MobileGL::MG_Backend::DirectGLES {
 
                 if (currentFBO.get() == lastUpdatedFBO) {
                     MGLOG_D("Draw FBO and read FBO are the same, skipping sync.");
+                    // The attachment/draw-buffer work was already done for this GL FBO as the DRAW
+                    // target, but the read buffer (glReadBuffer) is READ-target-specific and would
+                    // be dropped by this skip. Apply it so reads target the right attachment (e.g.
+                    // KHR-GL33.draw_buffers reads each COLOR_ATTACHMENT while the FBO stays bound as
+                    // GL_FRAMEBUFFER — without this every glReadBuffer is a no-op and all reads hit
+                    // COLOR_ATTACHMENT0).
+                    if (target == FramebufferTarget::Read) {
+                        const auto& syncedFBOIt = g_backendFramebufferObjects.find(currentFBO.get());
+                        if (syncedFBOIt != g_backendFramebufferObjects.end() && syncedFBOIt->second) {
+                            syncedFBOIt->second->SyncReadBufferToBackend(currentFBO);
+                        }
+                    }
                     g_fboSyncedObjectVersions[SizeT(target)] = objectVersion;
                     g_fboSyncedObjects[SizeT(target)] = currentPtr;
                     continue;