refactor(snap): widen snap_pts to f64 (world_offset removal P2)

WireModel/LocalWire/TruckEntity snap buffers and the producers/consumers
now carry snap candidates as DVec3 (offset_snap_pts, dimension/multileader
producers, block-cache transform, pick/xclip, snap module). Still
offset-relative, so behaviour is unchanged — this just lets the snap
transport survive the upcoming switch to absolute coordinates without an
extra f32 quantization. The snap module still resolves in f32 (as_vec3 at
entry), matching today's precision.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/entities/dimension.rs

@@ -1837,12 +1837,12 @@ fn append_angular_dimension(
     }
 }
 
-fn dimension_snap_pts(dim: &Dimension, world_offset: [f64; 3]) -> Vec<(Vec3, SnapHint)> {
+fn dimension_snap_pts(dim: &Dimension, world_offset: [f64; 3]) -> Vec<(glam::DVec3, SnapHint)> {
     let lv = |v: acadrust::types::Vector3| {
-        Vec3::new(
-            (v.x - world_offset[0]) as f32,
-            (v.y - world_offset[1]) as f32,
-            (v.z - world_offset[2]) as f32,
+        glam::DVec3::new(
+            v.x - world_offset[0],
+            v.y - world_offset[1],
+            v.z - world_offset[2],
         )
     };
     let node = |v: acadrust::types::Vector3| (lv(v), SnapHint::Node);