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/offset.rs

@@ -18,7 +18,7 @@ use acadrust::entities::{
     Spline as SplineEnt,
 };
 use acadrust::{EntityType, Handle};
-use glam::Vec3;
+use glam::{DVec3, Vec3};
 
 use crate::command::{CadCommand, CmdResult};
 use crate::modules::draw::defaults;
@@ -632,7 +632,7 @@ impl CadCommand for OffsetCommand {
         matches!(self.step, Step::SelectObject)
     }
 
-    fn on_entity_pick(&mut self, handle: Handle, _pt: Vec3) -> CmdResult {
+    fn on_entity_pick(&mut self, handle: Handle, _pt: DVec3) -> CmdResult {
         if handle.is_null() || !matches!(self.step, Step::SelectObject) {
             return CmdResult::NeedPoint;
         }
@@ -672,10 +672,10 @@ impl CadCommand for OffsetCommand {
         }
     }
 
-    fn dyn_live_value(&self, cursor: Vec3) -> Option<f64> {
+    fn dyn_live_value(&self, cursor: DVec3) -> Option<f64> {
         match &self.step {
             Step::PickSide { entity, locked, .. } => {
-                Some(locked.unwrap_or_else(|| perp_distance(entity, cursor)))
+                Some(locked.unwrap_or_else(|| perp_distance(entity, cursor.as_vec3())))
             }
             _ => None,
         }
@@ -697,7 +697,7 @@ impl CadCommand for OffsetCommand {
         None
     }
 
-    fn on_hover_entity(&mut self, handle: Handle, _pt: Vec3) -> Vec<WireModel> {
+    fn on_hover_entity(&mut self, handle: Handle, _pt: DVec3) -> Vec<WireModel> {
         if handle.is_null() {
             return vec![];
         }
@@ -719,33 +719,33 @@ impl CadCommand for OffsetCommand {
         vec![]
     }
 
-    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+    fn on_point(&mut self, pt: DVec3) -> CmdResult {
         let (locked, entity) = match &self.step {
             Step::PickSide { locked, entity, .. } => (*locked, entity.clone()),
             _ => return CmdResult::NeedPoint,
         };
-        let mag = locked.unwrap_or_else(|| perp_distance(&entity, pt));
+        let mag = locked.unwrap_or_else(|| perp_distance(&entity, pt.as_vec3()));
         if mag < 1e-9 {
             return CmdResult::NeedPoint;
         }
 
-        match compute_offset(&entity, mag, pt) {
+        match compute_offset(&entity, mag, pt.as_vec3()) {
             Some(new_entity) => CmdResult::CommitAndExit(new_entity),
             None => CmdResult::NeedPoint,
         }
     }
 
-    fn on_preview_wires(&mut self, pt: Vec3) -> Vec<WireModel> {
+    fn on_preview_wires(&mut self, pt: DVec3) -> Vec<WireModel> {
         let (locked, entity) = match &self.step {
             Step::PickSide { locked, entity, .. } => (*locked, entity.clone()),
             _ => return vec![],
         };
-        let mag = locked.unwrap_or_else(|| perp_distance(&entity, pt));
+        let mag = locked.unwrap_or_else(|| perp_distance(&entity, pt.as_vec3()));
         if mag < 1e-9 {
             return vec![];
         }
 
-        if let Some(result) = compute_offset(&entity, mag, pt) {
+        if let Some(result) = compute_offset(&entity, mag, pt.as_vec3()) {
             let pts = entity_wire_pts(&result);
             if !pts.is_empty() {
                 return vec![WireModel::solid(