native renderer: game world at MT_RENDER_SCALE (0.75 on Android), MSAA default 2

Draws recorded inside CPythonApplication::RenderGame are marked Render3DDraw::scene and
drawn by a scene pass compatible with pass_ into a reduced-resolution image, composited
where RenderGame drew; the UI stays full resolution. --render-scale / MT_RENDER_SCALE,
desktop default 1.0 (unchanged path).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/host/vk_pipelines.cpp

@@ -92,6 +92,7 @@ void VulkanWindow::create_render_pass_and_layout() {
 
     get_pipeline(0, 2, 0);
     create_offscreen_pass();
+    create_scene_pass();
 }
 
 void VulkanWindow::create_offscreen_pass() {