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/layout/mview.rs

@@ -11,7 +11,7 @@ use acadrust::EntityType;
 use crate::command::{CadCommand, CmdResult};
 use crate::modules::{IconKind, ModuleEvent, ToolDef};
 use crate::scene::model::wire_model::WireModel;
-use glam::Vec3;
+use glam::{DVec3, Vec3};
 
 // ── Ribbon definition ─────────────────────────────────────────────────────
 
@@ -49,7 +49,7 @@ impl CadCommand for MviewCommand {
         }
     }
 
-    fn on_point(&mut self, pt: Vec3) -> CmdResult {
+    fn on_point(&mut self, pt: DVec3) -> CmdResult { let pt = pt.as_vec3();
         if let Some(c1) = self.corner1 {
             let w = (pt.x - c1.x).abs() as f64;
             let h = (pt.y - c1.y).abs() as f64;
@@ -77,7 +77,7 @@ impl CadCommand for MviewCommand {
         CmdResult::Cancel
     }
 
-    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();
         let c1 = self.corner1?;
         Some(WireModel {
             name: "mview_preview".to_string(),