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/draw/modify/copy.rs

@@ -6,7 +6,7 @@
 //   Step 2+: each click makes another copy at (click - base); Enter to finish.
 
 use acadrust::Handle;
-use glam::Vec3;
+use glam::DVec3;
 
 use crate::command::{CadCommand, CmdResult, EntityTransform};
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
@@ -27,7 +27,7 @@ pub fn tool() -> ToolDef {
 
 enum Step {
     Base,
-    Placing(Vec3),
+    Placing(DVec3),
 }
 
 pub struct CopyCommand {
@@ -66,7 +66,7 @@ impl CadCommand for CopyCommand {
         }
     }
 
-    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+    fn on_point(&mut self, pt: DVec3) -> CmdResult {
         match &self.step {
             Step::Base => {
                 self.step = Step::Placing(pt);
@@ -87,7 +87,7 @@ impl CadCommand for CopyCommand {
         CmdResult::Cancel
     }
 
-    fn on_preview_wires(&mut self, pt: Vec3) -> Vec<WireModel> {
+    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
         let Step::Placing(base) = &self.step else {
             return vec![];
         };
@@ -95,11 +95,14 @@ impl CadCommand for CopyCommand {
         let mut out: Vec<WireModel> = self
             .wire_models
             .iter()
-            .map(|w| w.translated(delta))
+            .map(|w| w.translated(delta.as_vec3()))
             .collect();
         out.push(WireModel::solid(
             "rubber_band".into(),
-            vec![[base.x, base.y, base.z], [pt.x, pt.y, pt.z]],
+            vec![
+                [base.x as f32, base.y as f32, base.z as f32],
+                [pt.x as f32, pt.y as f32, pt.z as f32],
+            ],
             WireModel::CYAN,
             false,
         ));