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/table.rs

@@ -139,8 +139,21 @@ impl TruckConvertible for Table {
             }
         }
 
+        // Table currently does its layout in glam::Vec3 (f32). The world_offset
+        // subtraction in tessellate.rs needs f64, so widen at the boundary —
+        // precision is already limited by the f32 math above (separate fix-up).
+        let pts_f64: Vec<[f64; 3]> = pts
+            .into_iter()
+            .map(|[x, y, z]| {
+                if x.is_nan() {
+                    [f64::NAN, f64::NAN, f64::NAN]
+                } else {
+                    [x as f64, y as f64, z as f64]
+                }
+            })
+            .collect();
         Some(TruckEntity {
-            object: TruckObject::Lines(pts),
+            object: TruckObject::Lines(pts_f64),
             snap_pts: vec![(origin, SnapHint::Insertion)],
             tangent_geoms: vec![],
             key_vertices: vec![],