feat(render): GPU analytical rendering for circles, arcs, and ellipses

- Render planar circles, circular arcs, ellipses, and elliptical arcs analytically via GPU-instanced screen-space quads and WGSL shaders.
- Implement exact arc sweep clamping with round end caps matching the CAD wire shader.
- Implement robust Newton-Raphson closest-point solver for ellipses with isotropic screen-space derivative anti-aliasing.
- Integrate into wire pipeline and PersistentWireArena upload paths.
- Remove unused mesh_volume_centroid function in doc_api.

src/scene/convert/tessellate.rs

@@ -707,9 +707,11 @@ pub fn tessellate(
     }
 
     // ── Try the kernel path first ───────────────────────────────────────────
+    // Zoom-adaptive circles scale their segment count from the current zoom level and radius.
     // Relative-PDSIZE points size their glyph from the current zoom so they
     // stay a roughly constant on-screen size; otherwise the header-driven path.
-    let te = crate::entities::point::relative_render(entity, document, world_per_pixel)
+    let te = crate::entities::circle::relative_render(entity, document, world_per_pixel)
+        .or_else(|| crate::entities::point::relative_render(entity, document, world_per_pixel))
         .or_else(|| crate::entities::light::relative_render(entity, document, world_per_pixel))
         .or_else(|| match entity {
             EntityType::Text(text) => Some(crate::entities::text::to_render_at_scale(