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 <[email protected]>

src/app/view/controls.rs

@@ -191,15 +191,15 @@ pub(super) fn viewport_controls<'a>(
 /// world position (and the base point for polar quantities).
 pub(super) fn dyn_component_value(
     f: &DynFieldEntry,
-    w: glam::Vec3,
-    base: Option<glam::Vec3>,
+    w: glam::DVec3,
+    base: Option<glam::DVec3>,
     xf: &super::super::helpers::UcsXform,
     comma_cartesian: bool,
 ) -> String {
     if let Some(b) = &f.buffer {
         return b.clone();
     }
-    let b = base.unwrap_or(glam::Vec3::ZERO);
+    let b = base.unwrap_or(glam::DVec3::ZERO);
     // Relative deltas and the polar angle read in the active UCS plane. The
     // delta is offset-invariant, so only the axis rotation matters (identity
     // xf reproduces the world-frame deltas).