refactor(snap): widen key_vertices to f64 (world_offset removal P4)

WireModel/LocalWire/BatchEntry key_vertices are now Vec<[f64; 3]>;
tessellation keeps them in f64 (no f32 cast at offset subtraction),
producers (dimension, leader, multileader) build them from the acadrust
f64 source, the block-cache transform keeps f64, and the face3d Face3D
quad path splits them into the double-single (high, low) pair. Consumers
(snap endpoint/midpoint, xclip) read via f32 at the leaf. Still
offset-relative (inert); endpoint/midpoint snap is no longer f32-capped.

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

src/entities/dimension.rs

@@ -1120,12 +1120,13 @@ fn tessellate_dimension_inner(
     };
 
     let snap_pts = dimension_snap_pts(dim, world_offset);
-    let key_vertices: Vec<[f32; 3]> = geom
+    let key_vertices: Vec<[f64; 3]> = geom
         .dim_lines
         .iter()
         .chain(geom.ext_lines.iter())
         .copied()
         .filter(|p| !(p[0].is_nan() || p[1].is_nan() || p[2].is_nan()))
+        .map(|[x, y, z]| [x as f64, y as f64, z as f64])
         .collect();
 
     // DIMLWD (dim line + arrows) and DIMLWE (extension lines). Negative

src/entities/leader.rs

@@ -623,7 +623,7 @@ impl LeaderTess for Leader {
 
         let mut points: Vec<[f32; 3]> = verts.iter().map(|v| p3(v)).collect();
         let mut tangents: Vec<TangentGeom> = Vec::new();
-        let key_vertices: Vec<[f32; 3]> = verts.iter().map(|v| p3(v)).collect();
+        let key_vertices: Vec<[f64; 3]> = verts.iter().map(|v| [v.x, v.y, v.z]).collect();
         let mut fill_tris: Vec<[f32; 3]> = Vec::new();
 
         for i in 0..verts.len().saturating_sub(1) {

src/entities/multileader.rs

@@ -1161,7 +1161,7 @@ impl MultiLeaderTess for MultiLeader {
 
         // ── Leader / arrow / dogleg points ───────────────────────────────────────
         let mut points: Vec<[f32; 3]> = Vec::new();
-        let mut key_verts: Vec<[f32; 3]> = Vec::new();
+        let mut key_verts: Vec<[f64; 3]> = Vec::new();
         let mut snap_pts: Vec<(glam::DVec3, SnapHint)> = Vec::new();
         let mut tangents: Vec<TangentGeom> = Vec::new();
         let mut arrow_fill: Vec<[f32; 3]> = Vec::new();
@@ -1209,7 +1209,7 @@ impl MultiLeaderTess for MultiLeader {
                         ctrl.push(cp_f);
                     }
                     for &c in &ctrl {
-                        key_verts.push(c);
+                        key_verts.push([c[0] as f64, c[1] as f64, c[2] as f64]);
                         snap_pts.push((Vec3::from(c).as_dvec3(), SnapHint::Node));
                     }