Put the renderer's two OS calls behind a seam master
Of the ~800 lines that create the D3D11 device, build the three pipelines and draw a frame, exactly two touch anything platform-specific: the display-size query and CreateSwapChainForCoreWindow. Both now go through render::SurfaceHost, and App.cpp supplies the WinRT half. This is the first cut of lifting the renderer out of the ref class. Nothing moves yet and no behaviour changes — the point is to name the boundary and show it is two calls wide, because that is the difference between a Steam native build being a port and being a rewrite. On PC the other side of this seam is CreateSwapChainForHwnd, which the GDK smoke already proved works against the same D3D11 device that D2D and DirectWrite share. ReadPackageBytes still resolves shaders and fonts through Windows.ApplicationModel.Package. That is named in the header rather than hidden: it belongs on platform::Paths, whose package() already answers it. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01XnG7gt9GQv3h9aZjLJtRHN