refactor(precision): widen command transform scalars and defaults to f64 (#311)

Completes the f64 migration on the CPU data path: the only f32 left now
is the GPU/render/screen layer, which is architecturally required (wgpu
vertex buffers and iced are f32; f64 vertices would double memory).

- EntityTransform::Rotate.angle_rad and Scale.factor are now f64 (the
  transform was already applied in f64 around the DVec3 center, so this
  only preserves the typed angle/factor). apply_standard_transform and
  apply_standard_scale take f64.
- CmdResult::ExtrudeEntity.height and AlignSelected.{angle_rad,scale}
  are f64; the EXTRUDE height parses as f64.
- defaults.rs (last-used construction values: circle radius/diameter,
  rotate angle, scale factor, offset/fillet/chamfer distance, array
  spacing/counts/angle) moved from Cell<f32> to Cell<f64>. Array counts
  round-trip through u32 (exact below 2^53).
- Consumers in circle/array/fillet/offset/rotate/scale/align/solid3d and
  dimension.rs rotate_point/scale_point follow. `as f32` is kept only
  where a value feeds a WireModel rubber-band/ghost (the preview path is
  screen-space f32).

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

src/modules/draw/modify/offset.rs

@@ -779,7 +779,7 @@ impl CadCommand for OffsetCommand {
             if !t.is_empty() {
                 if let Ok(d) = t.parse::<f64>() {
                     let d = d.abs().max(1e-9);
-                    defaults::set_offset_dist(d as f32);
+                    defaults::set_offset_dist(d);
                     *locked = Some(d);
                 }
             }