fix: grid lines for split ruling edges only in display and export meshes; record the moved seeds (#961)

#921's grid lines through the vertices that split a ruling edge also went into the meshes Boolean operations intersect, which changed seven robustness seeds (seed 2's sphere cut failed). Deflection::rulings now asks for them only in the kernel's own tessellation (display, export, measurement). The seeds #936 (rejected instead of unsupported), #946 (26 and 85 build, others fail differently) and #921's display side (about 1e-6) moved are recorded with their reasons.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/kernel/src/body.rs

@@ -173,7 +173,7 @@ const MIN_DISPLAY_ANGLE: f64 = std::f64::consts::PI / 180.0;
 /// non-manifold shells an import can produce). Boundaries that lie on their surface only within
 /// tolerance (imports, boolean results) are projected onto it.
 fn mesh_shells(solid: &Solid, tol: f64) -> Vec<MeshedShell> {
-    mesh_shells_within(solid, Deflection::chord(tol))
+    mesh_shells_within(solid, Deflection { rulings: true, ..Deflection::chord(tol) })
 }
 
 /// [`mesh_shells`] divided by a chord tolerance and, when it has one, a bound on the angle a
@@ -986,9 +986,9 @@ impl Body {
             return Ok(m.to_mesh());
         }
         let deflection = if angle.is_finite() && angle > 0.0 {
-            Deflection { chord: tol, angle: angle.max(MIN_DISPLAY_ANGLE), floor: tol * DISPLAY_ANGLE_FLOOR }
+            Deflection { chord: tol, angle: angle.max(MIN_DISPLAY_ANGLE), floor: tol * DISPLAY_ANGLE_FLOOR, rulings: true }
         } else {
-            Deflection::chord(tol)
+            Deflection { rulings: true, ..Deflection::chord(tol) }
         };
         guard("tessellate", || {
             let meshed = mesh_shells_within(&self.solid, deflection);