Window::OnResized() (called for every SDL window-resize event, including
entering/leaving browser fullscreen) updated the window's own tracked
pixel size but never propagated it to the window's back buffer render
target, whose stale size kept driving glViewport() - so toggling
fullscreen resized the canvas but rendering stayed pinned to the old,
smaller viewport. Mirrors the resize handling the BGFX backend already
does explicitly elsewhere in RenderDevice.cpp.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
