wgpu: overlay points (sprite-style, quad-expanded with stroke halo)

Ports GL OverlayRenderer's setOverlayPoints API to WgpuOverlayRenderer.
Each point becomes a 6-vertex screen-space quad sized to inner_diameter
+ 2*stroke_extra; the fragment reads its per-vertex corner varying
instead of gl_PointCoord (WebGPU has no sized-point primitive). Sharp
inner/stroke transition + AA on the outer edge only, matching GL.

Single uniform slot per set — colors are global to the call, not per
point. Vertex buffer regrows 1.5× on demand so steady-state sets don't
re-allocate.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ifcviewer-wgpu/WgpuViewportWindow.cpp

@@ -2837,6 +2837,18 @@ void WgpuViewportWindow::setOverlayLines(
     if (isExposed()) requestUpdate();
 }
 
+void WgpuViewportWindow::setOverlayPoints(const std::vector<float>& world_xyz,
+                                          float r, float g, float b, float a,
+                                          float pixel_size,
+                                          float stroke_r, float stroke_g,
+                                          float stroke_b, float stroke_a,
+                                          float stroke_extra) {
+    overlays_.setOverlayPoints(world_xyz, r, g, b, a, pixel_size,
+                               stroke_r, stroke_g, stroke_b, stroke_a,
+                               stroke_extra);
+    if (isExposed()) requestUpdate();
+}
+
 // Project a world point to LOGICAL pixel coords (Qt's mouse-event units).
 // Returns false if behind the camera.
 static bool projectWorldToLogicalScreen(const QMatrix4x4& vp,
@@ -3954,6 +3966,11 @@ void WgpuViewportWindow::render() {
     // them on the resolved surface afterwards.
     overlays_.encodeOverlayLines(pass, overlay_frame);
 
+    // Overlay point sprites (measurement endpoints, snap candidates).
+    // Drawn after lines so the sprite halo correctly covers any line
+    // ends at the same world position.
+    overlays_.encodeOverlayPoints(pass, overlay_frame);
+
     wgpuRenderPassEncoderEnd(pass);
     wgpuRenderPassEncoderRelease(pass);