WgpuViewportWindow.cpp had ~1100 lines of pipeline/shader/buffer plumbing
for the axis indicator, pivot gizmo, section visualizer, and marquee
drag rect. Mirroring the GL backend's split, that lives in its own class
now; the viewport keeps the camera/cull/draw loop and hands the renderer
a per-frame WgpuOverlayFrame snapshot for each encode call.
No behavioural change — pixel-identical screenshot on basic.ifcview.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Dion Moult