Port the PlanarEllipse tangent-geom variant and full OSNAP ellipse fix

Completes the OSNAP intersection port from 44deee2a: that commit
explicitly deferred ellipse support because this branch's TangentGeom
predates the PlanarEllipse variant added upstream (this branch was cut
from an older main snapshot, ~99 commits behind on unrelated work).
Ports just the variant and its minimal direct dependents, not the
other unrelated evolution in those 99 commits (a separate analytical
GPU fast-path for circle/arc/ellipse rendering, tessellation changes,
etc. — out of scope here).

- wire_model.rs: copied verbatim from main. Restores the
  PlanarEllipse variant plus TangentGeom's translated/rotated/scaled/
  mirrored methods (this branch was missing all four transform methods
  entirely, not just ellipse support in them — a live-drag preview
  wire's tangent_geoms weren't being updated at all during a
  translate/rotate/scale/mirror preview).
- entities/ellipse.rs: restored building the PlanarEllipse tangent_geom
  for a committed ellipse/elliptical-arc entity's RenderEntity — this
  is what makes ellipses queryable by OSNAP at all (the resident wire
  set is what Intersection/Tangent snap search).
- entities/dimension.rs, scene/cache/block_cache.rs: added back the
  three PlanarEllipse match arms needed for exhaustiveness (OCS-to-WCS
  remapping, prototype-wire translation, and instance-transform
  application) — each a self-contained arm restoring exactly the
  ellipse case, not touching the surrounding logic.
- snap.rs: replaced with the exact fix from the upstream PR (HakanSeven12/OpenCADStudio#1104)
  branch, whose snap.rs was already verified to differ from main by
  nothing but that fix. Upgrades the earlier circle/arc-only port to
  the full exact_curve_intersections path: line-vs-circle/arc/ellipse
  and ellipse-vs-circle/arc/ellipse, via cadkernel::geom2d::intersect
  over a shared embedding plane, including the anti-parallel-normal
  reflection fix for both Arc and PlanarEllipse.

7 additional tests now build and pass (line/ellipse intersection
cases, both anti-parallel-normal regressions) plus the wire-transform
test wire_model.rs already carried. Full workspace suite passes except
the one pre-existing, unrelated font-test failure also present on
main.

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

src/entities/dimension.rs

@@ -5408,6 +5408,21 @@ fn map_wire_ocs_to_wcs(wire: &mut WireModel, normal: Vector3) {
                 *axis_x = map_vector(*axis_x);
                 *axis_y = map_vector(*axis_y);
             }
+            TangentGeom::PlanarEllipse {
+                center,
+                major_axis,
+                normal,
+                ..
+            } => {
+                let mapped = map(center[0], center[1], center[2]);
+                let map_vector = |axis: [f64; 3]| {
+                    let mapped = map(axis[0], axis[1], axis[2]);
+                    [mapped.0, mapped.1, mapped.2]
+                };
+                *center = [mapped.0, mapped.1, mapped.2];
+                *major_axis = map_vector(*major_axis);
+                *normal = map_vector(*normal);
+            }
         }
     }
     wire.aabb = WireModel::UNBOUNDED_AABB;

src/entities/ellipse.rs

@@ -15,6 +15,7 @@ use crate::entities::common::{
 use crate::entities::traits::RenderConvertible;
 use crate::scene::convert::acad_to_render::{RenderEntity, RenderObject};
 use crate::scene::model::object::{GripApply, GripDef, PropSection};
+use crate::scene::model::wire_model::TangentGeom;
 
 fn to_render(ell: &Ellipse) -> RenderEntity {
     // ELLIPSE is one of the few WCS entities in DXF: `center` (code 10) and
@@ -29,6 +30,15 @@ fn to_render(ell: &Ellipse) -> RenderEntity {
         .map(crate::entities::curve::snap_from)
         .unwrap_or_default();
 
+    let tangent = TangentGeom::PlanarEllipse {
+        center: [ell.center.x, ell.center.y, ell.center.z],
+        major_axis: [ell.major_axis.x, ell.major_axis.y, ell.major_axis.z],
+        normal: [ell.normal.x, ell.normal.y, ell.normal.z],
+        minor_axis_ratio: ell.minor_axis_ratio,
+        start_param: ell.start_parameter,
+        end_param: ell.end_parameter,
+    };
+
     // The points come from the entity's own kernel curve and angular policy.
     //
     // What does not change is the shape of the object. EXTRUDE, REVOLVE and
@@ -39,7 +49,7 @@ fn to_render(ell: &Ellipse) -> RenderEntity {
         pick_tris: Vec::new(),
         object: RenderObject::Lines(Vec::new()),
         snap_pts: snap.snap_pts,
-        tangent_geoms: vec![],
+        tangent_geoms: vec![tangent.clone()],
         key_vertices: vec![],
         fill_tris: vec![],
     };
@@ -57,7 +67,7 @@ fn to_render(ell: &Ellipse) -> RenderEntity {
         pick_tris: Vec::new(),
         object,
         snap_pts: snap.snap_pts,
-        tangent_geoms: vec![],
+        tangent_geoms: vec![tangent],
         key_vertices: vec![],
         fill_tris: vec![],
     }