fix(render): preserve f64 precision until world_offset subtraction

Entity converters were casting WCS coordinates to f32 before the renderer
subtracted world_offset, which destroyed sub-unit precision on drawings
sitting at large coordinates (typical UTM-style CAD files). The multileader
case made it visible — glyphs warped under rotation — but every entity
that emits TruckObject::Lines/SegmentedLines/key_vertices/fill_tris was
affected.

Type changes (in src/scene/acad_to_truck.rs):
- TruckObject::Lines / SegmentedLines: Vec<[f32; 3]> → Vec<[f64; 3]>
- TruckEntity::key_vertices / fill_tris: f32 → f64

All ~17 producer files updated to keep WCS coordinates in f64 right up to
the TruckEntity boundary. The consumer in scene/tessellate.rs now performs
`(x - ox) as f32` (f64 subtract, then cast) for points, key_vertices, and
fill_tris — preserving precision near the camera origin even when the
drawing sits at million-unit coordinates.

catmull_rom_pts (multileader spline) is now f64; the scene path widens its
offset-relative f32 ctrl points to f64 around the call and narrows back at
the output.

Notes:
- Table layout still uses glam::Vec3 (f32) internally; widened to f64 only
  at the TruckEntity boundary for type compatibility. Separate cleanup to
  switch its internal math to f64 is tracked.
- snap_pts and tangent_geoms remain f32 — they are UI feedback (snap
  candidates, tangent hints) and the precision is sufficient there.

src/entities/circle.rs

@@ -69,31 +69,23 @@ fn to_truck(circle: &Circle) -> TruckEntity {
                 cwz + r * (c * ax.2 + s * ay.2),
             )
         };
-        let mut pts: Vec<[f32; 3]> = Vec::with_capacity((n + 1) * 2 + 4 * 3);
+        let mut pts: Vec<[f64; 3]> = Vec::with_capacity((n + 1) * 2 + 4 * 3);
         for i in 0..=n {
             let (x, y, z) = circ_pt(i as f64 * tau / n as f64);
-            pts.push([x as f32, y as f32, z as f32]);
+            pts.push([x, y, z]);
         }
-        pts.push([f32::NAN; 3]);
+        pts.push([f64::NAN; 3]);
         for i in 0..=n {
             let (x, y, z) = circ_pt(i as f64 * tau / n as f64);
-            pts.push([
-                (x + t * nx) as f32,
-                (y + t * ny) as f32,
-                (z + t * nz) as f32,
-            ]);
+            pts.push([x + t * nx, y + t * ny, z + t * nz]);
         }
-        pts.push([f32::NAN; 3]);
+        pts.push([f64::NAN; 3]);
         for i in 0..4usize {
             let (x, y, z) = circ_pt(i as f64 * std::f64::consts::FRAC_PI_2);
-            pts.push([x as f32, y as f32, z as f32]);
-            pts.push([
-                (x + t * nx) as f32,
-                (y + t * ny) as f32,
-                (z + t * nz) as f32,
-            ]);
+            pts.push([x, y, z]);
+            pts.push([x + t * nx, y + t * ny, z + t * nz]);
             if i < 3 {
-                pts.push([f32::NAN; 3]);
+                pts.push([f64::NAN; 3]);
             }
         }
         return TruckEntity {