feat(f64): command layer compiles on DVec3

Whole command/snap/grip/cursor chain now builds on f64 DVec3 end to end,
so picked points, snaps and grip drags stay precise at UTM-scale
coordinates instead of quantizing to ~0.5 m through f32.

- All ~80 command files migrated: draw (line/circle/arc/ellipse/shapes
  in full f64; others via point methods), modify, annotate, insert, view,
  inquiry, layers, groups, clipboard, layout.
- Entity apply_grip impls updated for GripApply::{Absolute,Translate}(DVec3).
- Construction sites (EntityTransform/CmdResult/DynAnchor) emit DVec3;
  wire-preview boundaries cast to f32 only at the GPU edge.
- Modify/annotate commands keep internal Vec3 geometry where precision is
  non-critical, casting at the DVec3 boundary; key draw commands store f64.

Builds clean (no warnings). Visual verification of crosshair/snap/grip at
extreme UTM zoom pending.

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

src/modules/model/primitive_cmd.rs

@@ -9,7 +9,7 @@
 
 use acadrust::entities::Solid3D;
 use acadrust::{primitives, EntityType};
-use glam::Vec3;
+use glam::{DVec3, Vec3};
 use truck_modeling::Solid;
 
 use crate::command::{CadCommand, CmdResult};
@@ -209,7 +209,7 @@ impl CadCommand for PrimitiveCommand {
         }
     }
 
-    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+    fn on_point(&mut self, pt: DVec3) -> CmdResult { let pt = pt.as_vec3();
         if self.height_step {
             // A click in the ground plane has no Z; use its distance from the
             // footprint centre as the height magnitude.
@@ -253,7 +253,7 @@ impl CadCommand for PrimitiveCommand {
         Some(self.commit(h))
     }
 
-    fn on_mouse_move(&mut self, pt: Vec3) -> Option<WireModel> {
+    fn on_mouse_move(&mut self, pt: DVec3) -> Option<WireModel> { let pt = pt.as_vec3();
         if self.height_step || self.pts.is_empty() {
             return None;
         }