refactor: drop truck, and evaluate every curve through the kernel

The last four truck crates are gone from the manifest. What they were doing
falls into three parts, and each now has one answer instead of two.

NURBS evaluation. truck was carrying B-spline curves and surfaces for the
SPLINE entity, hatch boundaries, BLEND's endpoint frames, the spline preview
and ACIS spline-surface faces. The kernel now has both, over one de Boor
written across however many coordinates a control point holds — so a plane
curve and a space curve cannot drift apart, and a surface is the same
algorithm applied twice. The rational and the polynomial cases stop being
separate types: weights absent means polynomial.

The entity conversion. Every LINE, ARC, ELLIPSE, SPLINE and polyline was
built into truck topology purely so it could be sampled back into points.
They are sampled through `entities::curve` now, which is where each one's
geometry is already defined once and what EXTRUDE and REVOLVE read — so a
circle drawn on screen and a circle handed to the Model tab come from the
same definition. That retires four of TruckObject's variants and the module
is renamed for what it does.

SWEEP and LOFT. Both only ever produced a mesh, so both are built from point
lists: a band of quads per span, and a lid where a profile closes. Lofting
profiles of different densities resamples them by distance rather than by
index, so a circle lofted to a square no longer twists.

Two things worth noting for anyone reading the old comments. The tolerance
globals that lived in the tessellation module were never about truck at all —
they are the per-frame chord height, and they move to `curve_tol`. And the
rule that a profile handed over as `Lines` silently broke EXTRUDE and REVOLVE
no longer holds: those read the curve directly and never look at this channel.

The two `automation` test failures are unchanged from before this and are not
caused by it.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/entities/light.rs

@@ -6,7 +6,7 @@
 //! same way AutoCAD shows a light symbol.
 //!
 //! The glyph is sized in **screen space** (a roughly constant pixel size across
-//! zoom) via [`relative_truck`], falling back to a small fixed world size when
+//! zoom) via [`relative_render`], falling back to a small fixed world size when
 //! no world-per-pixel factor is available (e.g. snapshot tessellation).
 
 use acadrust::entities::Light;
@@ -17,8 +17,8 @@ use crate::command::EntityTransform;
 use crate::entities::common::{
     center_grip, edit_angle_prop, edit_prop as edit, ro_prop, square_grip,
 };
-use crate::entities::traits::{Grippable, PropertyEditable, Transformable, TruckConvertible};
-use crate::scene::convert::acad_to_truck::{TruckEntity, TruckObject};
+use crate::entities::traits::{Grippable, PropertyEditable, Transformable, RenderConvertible};
+use crate::scene::convert::acad_to_render::{RenderEntity, RenderObject};
 use crate::scene::model::object::{GripApply, GripDef, PropSection, PropValue, Property};
 use crate::scene::model::wire_model::SnapHint;
 
@@ -165,7 +165,7 @@ fn light_wire(l: &Light, r: f64) -> Vec<[f64; 3]> {
     out
 }
 
-fn build(l: &Light, r: f64) -> TruckEntity {
+fn build(l: &Light, r: f64) -> RenderEntity {
     let p = pos(l);
     let snap = glam::DVec3::new(p[0], p[1], p[2]);
     let mut snap_pts = vec![(snap, SnapHint::Node)];
@@ -175,9 +175,9 @@ fn build(l: &Light, r: f64) -> TruckEntity {
         snap_pts.push((glam::DVec3::new(t[0], t[1], t[2]), SnapHint::Node));
         key.push(t);
     }
-    TruckEntity {
+    RenderEntity {
         pick_tris: Vec::new(),
-        object: TruckObject::Lines(light_wire(l, r)),
+        object: RenderObject::Lines(light_wire(l, r)),
         snap_pts,
         tangent_geoms: vec![],
         key_vertices: key,
@@ -187,12 +187,12 @@ fn build(l: &Light, r: f64) -> TruckEntity {
 
 /// Viewport-aware glyph: constant on-screen size from the world-per-pixel
 /// factor. Returns `None` for a non-light entity or when no factor is
-/// available (the caller then falls back to the fixed-world [`to_truck`]).
-pub fn relative_truck(
+/// available (the caller then falls back to the fixed-world [`to_render`]).
+pub fn relative_render(
     entity: &EntityType,
     _document: &acadrust::CadDocument,
     wpp: Option<f32>,
-) -> Option<TruckEntity> {
+) -> Option<RenderEntity> {
     let EntityType::Light(l) = entity else {
         return None;
     };
@@ -200,8 +200,8 @@ pub fn relative_truck(
     Some(build(l, w * GLYPH_PX))
 }
 
-impl TruckConvertible for Light {
-    fn to_truck(&self, _document: &acadrust::CadDocument) -> Option<TruckEntity> {
+impl RenderConvertible for Light {
+    fn to_render(&self, _document: &acadrust::CadDocument) -> Option<RenderEntity> {
         Some(build(self, FIXED_WORLD))
     }
 }