Ports GL OverlayRenderer's LineGroup API to WgpuOverlayRenderer. Each
group's segments are CPU-expanded into screen-space quads; the WGSL
fragment reproduces the GL pixel-distance stroke pick + arc-length
dash logic. One uniform slot per group, bound via dynamic offset so a
single bind-group services up to N groups.
No caller yet — sets up the API the wgpu measure tools (task #29) will
use. WgpuViewportWindow.setOverlayLines mirrors the GL viewport's
signature so the bonsai Measurement code can target either backend
through one interface.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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