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/entities/hatch.rs

@@ -188,9 +188,9 @@ impl Grippable for Hatch {
         fn resolve(apply: &GripApply, cur: Vec3) -> (f64, f64) {
             let p = match apply {
                 GripApply::Absolute(p) => *p,
-                GripApply::Translate(d) => cur + *d,
+                GripApply::Translate(d) => cur.as_dvec3() + *d,
             };
-            (p.x as f64, p.y as f64)
+            (p.x, p.y)
         }
 
         'outer: for path in &mut self.paths {