feat(render): render thick and tapered analytical arcs directly on GPU

- Repurpose CircleInstance center_high.w and params.w for start_width and end_width (preserving exact 128-byte stride)
- Route wide polylines, tapered polylines with bulges, and donuts through split_mixed_polyline into GPU analytical arc instances
- Compute physical annular bands, width tapers, and round end caps in circle.wgsl using world-space distances to prevent 3D perspective foreshortening distortion
- Expand bounding quad margins dynamically with grazing-angle compensation to eliminate clipping
- Relax pick_tris check in wire classification and partition routines so wide entities retain CPU picking while drawing analytically
- Add unit and hardware GPU integration tests, including tilted 3D perspective rendering verification

src/modules/draw/draw/donut.rs

@@ -253,7 +253,7 @@ fn donut_wire(
     WireModel::solid_f64("rubber_band".into(), points, WireModel::CYAN, false)
 }
 
-fn make_donut(cx: f64, cy: f64, elevation: f64, inner_r: f64, outer_r: f64) -> EntityType {
+pub(crate) fn make_donut(cx: f64, cy: f64, elevation: f64, inner_r: f64, outer_r: f64) -> EntityType {
     use acadrust::types::Vector2;
     let r_avg = (inner_r + outer_r) / 2.0;
     let width = outer_r - inner_r;