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 <[email protected]>

src/scene/cache/block_cache.rs

@@ -39,7 +39,7 @@ pub struct LocalWire {
     /// sub-f32 precision once the renderer translates them to world space.
     pub points_low: Vec<[f32; 3]>,
     pub key_vertices: Vec<[f32; 3]>,
-    pub snap_pts: Vec<(glam::Vec3, SnapHint)>,
+    pub snap_pts: Vec<(glam::DVec3, SnapHint)>,
     pub tangent_geoms: Vec<TangentGeom>,
     pub fill_tris: Vec<[f32; 3]>,
     pub color: [f32; 4],
@@ -1041,7 +1041,7 @@ struct BatchEntry {
     plinegen: bool,
     points: Vec<[f32; 3]>,
     points_low: Vec<[f32; 3]>,
-    snap_pts: Vec<(glam::Vec3, SnapHint)>,
+    snap_pts: Vec<(glam::DVec3, SnapHint)>,
     key_vertices: Vec<[f32; 3]>,
     tangent_geoms: Vec<TangentGeom>,
     fill_tris: Vec<[f32; 3]>,
@@ -1465,11 +1465,7 @@ fn emit_wire(
             p.z as f64 + lo_z,
         ));
         entry.snap_pts.push((
-            glam::Vec3::new(
-                (v.x - ox) as f32,
-                (v.y - oy) as f32,
-                (v.z - oz) as f32,
-            ),
+            glam::DVec3::new(v.x - ox, v.y - oy, v.z - oz),
             *hint,
         ));
     }

src/scene/convert/tessellate.rs

@@ -477,7 +477,7 @@ pub fn tessellate(
                 // Add insertion snap at point_of_reference.
                 let [ox, oy, oz] = world_offset;
                 if let Some(p) = crate::entities::solid3d::point_of_reference(entity) {
-                    let sp = Vec3::new((p.x - ox) as f32, (p.y - oy) as f32, (p.z - oz) as f32);
+                    let sp = glam::DVec3::new(p.x - ox, p.y - oy, p.z - oz);
                     wm.snap_pts.push((sp, SnapHint::Insertion));
                 }
                 return vec![wm];
@@ -487,6 +487,10 @@ pub fn tessellate(
 
     // ── Fallback for Viewport / Insert / Hatch / Ole2Frame ────────────────
     let (points, snap_pts, tangent_geoms, key_vertices) = fallback_geometry(entity, world_offset);
+    // fallback_geometry still emits offset-relative f32 snap points; widen to
+    // f64 for the WireModel's double-single-era snap buffer.
+    let snap_pts: Vec<(glam::DVec3, SnapHint)> =
+        snap_pts.into_iter().map(|(p, h)| (p.as_dvec3(), h)).collect();
     vec![WireModel {
         name,
         points,
@@ -858,12 +862,15 @@ pub(crate) fn add_polyline(points: &mut Vec<[f32; 3]>, polyline: &[Vec3]) {
     points.extend(polyline.iter().map(|p| [p.x, p.y, p.z]));
 }
 
-pub(crate) fn offset_snap_pts(pts: Vec<(Vec3, SnapHint)>, off: [f64; 3]) -> Vec<(Vec3, SnapHint)> {
+pub(crate) fn offset_snap_pts(
+    pts: Vec<(Vec3, SnapHint)>,
+    off: [f64; 3],
+) -> Vec<(glam::DVec3, SnapHint)> {
     let [ox, oy, oz] = off;
     pts.into_iter()
         .map(|(p, h)| {
             (
-                Vec3::new(p.x - ox as f32, p.y - oy as f32, p.z - oz as f32),
+                glam::DVec3::new(p.x as f64 - ox, p.y as f64 - oy, p.z as f64 - oz),
                 h,
             )
         })

src/scene/mod.rs

@@ -8229,7 +8229,7 @@ fn tessellate_entity(
             pattern_length: 0.0,
             pattern: [0.0; 8],
             line_weight_px: 1.0,
-            snap_pts: vec![(ip, model::wire_model::SnapHint::Insertion)],
+            snap_pts: vec![(ip.as_dvec3(), model::wire_model::SnapHint::Insertion)],
             tangent_geoms: vec![],
             key_vertices: vec![],
             aabb: WireModel::UNBOUNDED_AABB,

src/scene/model/wire_model.rs

@@ -57,7 +57,7 @@ pub struct WireModel {
     /// ACI color index (1-255).  0 means true-color or unknown (no CTB lookup).
     pub aci: u8,
     /// Pre-baked snap candidates (Center, Node, Quadrant, Insertion).
-    pub snap_pts: Vec<(glam::Vec3, SnapHint)>,
+    pub snap_pts: Vec<(glam::DVec3, SnapHint)>,
     /// Per-segment tangent geometry for Tangent snap.
     /// Line/Arc entities: 1 entry.  LwPolyline: 1 entry per segment.
     pub tangent_geoms: Vec<TangentGeom>,

src/scene/pick/xclip.rs

@@ -104,7 +104,7 @@ pub fn clip_wires(wires: &mut Vec<WireModel>, poly: &[[f32; 2]]) {
         }
         w.key_vertices
             .retain(|v| point_in_poly(v[0], v[1], poly));
-        w.snap_pts.retain(|(p, _)| point_in_poly(p.x, p.y, poly));
+        w.snap_pts.retain(|(p, _)| point_in_poly(p.x as f32, p.y as f32, poly));
         w.aabb = recompute_aabb(&w.points, &w.fill_tris);
     }
     wires.retain(|w| !w.points.is_empty() || !w.fill_tris.is_empty());