Extend GPU analytical circle and arc rendering to block inserts

- Emit transformed analytical curves (circles, arcs, ellipses) in block
  expansion as standalone wires rather than merging them into batched line
  strips.
- Keep render_instance unset on analytical curves in block prototypes so
  they route directly to CircleGpu / EllipseGpu instead of BlockWireGpu.
- Support TangentGeom::Circle in extract_circle_instance and wire partitioning.
- Drop analytical tangents on wires clipped by xclip so clipped geometry
  falls back correctly to line segments.
- Add unit test verifying block circles and arcs extract as analytical GPU
  instances.

src/scene/pipeline/wire_arena.rs

@@ -150,7 +150,8 @@ pub fn classify_wire(wire: &WireModel) -> WireKind {
         && wire.text_verts.is_empty()
     {
         match &wire.tangent_geoms[0] {
-            crate::scene::model::wire_model::TangentGeom::PlanarCircle { .. }
+            crate::scene::model::wire_model::TangentGeom::Circle { .. }
+            | crate::scene::model::wire_model::TangentGeom::PlanarCircle { .. }
             | crate::scene::model::wire_model::TangentGeom::Arc { .. } => {
                 if super::circle_gpu::extract_circle_instance(wire, 0.0).is_some() {
                     return WireKind::Circle;
@@ -214,7 +215,8 @@ pub fn partition_wires<'a>(
             && wire.text_verts.is_empty()
         {
             match &wire.tangent_geoms[0] {
-                crate::scene::model::wire_model::TangentGeom::PlanarCircle { .. }
+                crate::scene::model::wire_model::TangentGeom::Circle { .. }
+                | crate::scene::model::wire_model::TangentGeom::PlanarCircle { .. }
                 | crate::scene::model::wire_model::TangentGeom::Arc { .. } => {
                     if let Some(inst) = super::circle_gpu::extract_circle_instance(wire, depth) {
                         circle_instances.push(inst);