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/app/commands.rs

@@ -5402,7 +5402,7 @@ impl OpenCADStudio {
                 if selected.len() == 1 {
                     let handle = selected[0].0;
                     let mut cmd = ExtrudeCommand::new(color);
-                    cmd.on_entity_pick(handle, glam::Vec3::ZERO);
+                    cmd.on_entity_pick(handle, glam::DVec3::ZERO);
                     self.command_line.push_info(&cmd.prompt());
                     self.tabs[i].active_cmd = Some(Box::new(cmd));
                 } else {
@@ -5931,7 +5931,7 @@ impl CadCommand for DrawOrderRefCommand {
     fn on_entity_pick(
         &mut self,
         handle: acadrust::Handle,
-        _pt: glam::Vec3,
+        _pt: glam::DVec3,
     ) -> crate::command::CmdResult {
         if handle.is_null() {
             return crate::command::CmdResult::NeedPoint;
@@ -5941,7 +5941,7 @@ impl CadCommand for DrawOrderRefCommand {
         crate::command::CmdResult::Relaunch(cmd, std::mem::take(&mut self.to_move))
     }
 
-    fn on_point(&mut self, _pt: glam::Vec3) -> crate::command::CmdResult {
+    fn on_point(&mut self, _pt: glam::DVec3) -> crate::command::CmdResult {
         crate::command::CmdResult::NeedPoint
     }