fix(precision): keep typed coordinates exact in f64 (#311)

Typed values were quantized to the f32 grid before reaching the
entity (e.g. a length of 2000.8 committed as 2000.8020), worsening
with magnitude. The interaction point layer was all glam::Vec3 (f32).

Two-layer fix:

1. Coordinate backbone -> f64. last_point, last_cursor_world,
   dyn_anchor, dyn_ref become DVec3; UcsXform transforms, parse_coord,
   the ucs helper fns, dyn_resolve_point, the OTRACK typed-distance
   paths, command-line coordinate entry and the coordinate readout all
   compute in f64. Screen/GPU/alignment stays f32 (snap engine, render
   geometry, projection, UCS-icon/viewcube drawing) with casts only at
   those boundaries.

2. Per-command committed storage -> DVec3. on_point already received a
   DVec3, but many command impls narrowed it back to f32 (let pt =
   pt.as_vec3(); Vec<Vec3> fields) and re-widened at build, quantizing
   the committed coordinate. Migrated PLINE, SPLINE, MLINE, LENGTHEN,
   INSERT, 3D primitives, every dimension/leader/mleader, ray, revcloud,
   wipeout, attdef, table, tolerance, array center, mview, plot_window,
   plus the QDIM_PLACE handler and qdim_collect_points. Preview,
   hit-test and rubber-band paths keep f32 at the boundary.

Hatch manual boundaries are left for a follow-up: HatchModel.boundary
is structurally Arc<Vec<[f32;2]>> and needs a model-level widen.

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

src/modules/draw/modify/torient.rs

@@ -6,7 +6,7 @@
 //   Step 2: If first point picked, pick second point to define angle vector.
 
 use acadrust::Handle;
-use glam::{DVec3, Vec3};
+use glam::DVec3;
 
 use crate::command::{CadCommand, CmdResult, DynField};
 use crate::scene::model::wire_model::WireModel;
@@ -16,7 +16,7 @@ use acadrust::EntityType;
 
 enum Step {
     AngleOrFirstPoint,
-    SecondPoint { first_point: Vec3 },
+    SecondPoint { first_point: DVec3 },
 }
 
 pub struct TorientCommand {
@@ -122,7 +122,7 @@ impl CadCommand for TorientCommand {
         }
     }
 
-    fn on_point(&mut self, pt: DVec3) -> CmdResult { let pt = pt.as_vec3();
+    fn on_point(&mut self, pt: DVec3) -> CmdResult {
         match self.step {
             Step::AngleOrFirstPoint => {
                 self.step = Step::SecondPoint { first_point: pt };
@@ -131,7 +131,7 @@ impl CadCommand for TorientCommand {
             Step::SecondPoint { first_point } => {
                 let dx = pt.x - first_point.x;
                 let dy = pt.y - first_point.y;
-                let angle = dy.atan2(dx) as f64;
+                let angle = dy.atan2(dx);
                 self.commit_angle(Some(angle))
             }
         }
@@ -157,8 +157,10 @@ impl CadCommand for TorientCommand {
         }
     }
 
-    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> { let pt = pt.as_vec3();
+    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
+        let pt = pt.as_vec3();
         if let Step::SecondPoint { first_point } = self.step {
+            let first_point = first_point.as_vec3();
             vec![WireModel::solid(
                 "rubber_band".into(),
                 vec![[first_point.x, first_point.y, first_point.z], [pt.x, pt.y, pt.z]],