New OverlayRenderer module owns every client-supplied overlay primitive
drawn after the main pass: tinted, depth-aware highlight triangles via
its own GL shader, and top-left HUD text via QPainter on a
QOpenGLPaintDevice. Public surface on ViewportWindow is just two
forwarders (setHighlightTriangles, setHudText).
ViewportWindow's MeshLocalPick now exposes the instance's composed
transform so consumers can map mesh-local geometry back to world
space without re-querying. AreaMeasurement uses both: its selection
key is now (object_id, tri) so per-instance highlighting works for
two distinct walls sharing a mesh, and on every pick it rebuilds the
world-space tri list and the HUD readout.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Dion Moult