fix(render): UTM-precise UCS icon + fallback outlines (hatch etc.)

Two UTM-scale rendering defects.

- UCS icon jittered: it projects only axis DIRECTIONS but went through the
  full view_proj, whose ~5.7e6 translation cancels catastrophically in f32.
  Feed it the rotation-only view_proj_rte instead (translation dropped).

- Fallback outline geometry (hatch boundary, viewport/insert/ole2frame
  frames, Solid3D edge wires) built absolute f32 points with an empty
  points_low, so at UTM the outline sat ~0.5 m off its own fill (the hatch
  fill renders precisely via the world_origin-relative HatchModel pipeline).
  FallbackGeometry now carries absolute f64 points + key vertices; the
  tessellate dispatcher splits them into the double-single high/low pair the
  relative-to-eye wire pass needs, so outlines land exactly on their fills.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/convert/tess_util.rs

@@ -16,11 +16,16 @@ use crate::scene::model::wire_model::{SnapHint, TangentGeom, WireModel};
 /// callsite when the dispatcher wraps these into a WireModel.
 ///
 /// Layout: `(points, snap_pts, tangent_geoms, key_vertices)`.
+///
+/// `points` are ABSOLUTE world coordinates in f64 — the dispatcher splits them
+/// into the double-single high/low pair the relative-to-eye renderer needs, so
+/// fallback outlines (hatch boundary, viewport/insert/ole2frame frames) stay
+/// glued to their fills at UTM scale instead of quantizing ~0.5 m in f32.
 pub type FallbackGeometry = (
-    Vec<[f32; 3]>,
+    Vec<[f64; 3]>,
     Vec<(Vec3, SnapHint)>,
     Vec<TangentGeom>,
-    Vec<[f32; 3]>,
+    Vec<[f64; 3]>,
 );
 
 // ── Arc tessellation helpers ─────────────────────────────────────────────