Tests: side-wall sag checks pick the wall by face, the dense-cluster test keeps its intent

The flat caps of a cylinder are their rim alone now, so a triangle with all corners on the
rim is no proof of a wall triangle: pick the wall's triangles by their face. The hole
placement test asserted the body had twice the face's triangles; it asserts the body has
other faces than the one picked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/doc/src/display_quality.rs

@@ -176,7 +176,12 @@ mod tests {
             let sag = mesh
                 .triangles
                 .iter()
-                .map(|t| t.map(|i| mesh.positions[i as usize]))
+                .zip(&mesh.tri_face)
+                // The side wall's own triangles: the flat caps have corners on the rim too.
+                .filter(|(_, f)| {
+                    matches!(solidcraft_kernel::face_surface(&mb.body, **f as usize), Some(solidcraft_kernel::FaceSurface::Cylinder { .. }))
+                })
+                .map(|(t, _)| t.map(|i| mesh.positions[i as usize]))
                 .filter(|t| t.iter().all(|p| (r(*p) - 20.0).abs() < 1e-9))
                 .map(|[a, b, c]| 20.0 - r((a + b + c) * (1.0 / 3.0)))
                 .fold(0.0, f64::max);

crates/ui-egui/src/display_lod.rs

@@ -468,7 +468,15 @@ mod tests {
         let sag = mesh
             .triangles
             .iter()
-            .map(|t| t.map(|i| mesh.positions[i as usize]))
+            .zip(&mesh.tri_face)
+            // The side wall's own triangles: the flat caps have corners on the rim too.
+            .filter(|(_, f)| {
+                matches!(
+                    solidcraft_engine::kernel::face_surface(&b.body, **f as usize),
+                    Some(solidcraft_engine::kernel::FaceSurface::Cylinder { .. })
+                )
+            })
+            .map(|(t, _)| t.map(|i| mesh.positions[i as usize]))
             .filter(|t| t.iter().all(|p| (r(*p) - 10.0).abs() < 1e-9))
             .map(|[a, b, c]| 10.0 - r((a + b + c) * (1.0 / 3.0)))
             .fold(0.0, f64::max);

crates/ui-egui/src/hole_placement_ui_tests.rs

@@ -785,7 +785,8 @@ fn cylinder_with_cluster(sketch: Value, at: [f64; 2], view: &str) -> Cluster {
         gap.x.max(gap.y).max(gap.z) <= 1e-3
     };
     let (body_tris, face_tris, near_tris) = (m.triangles.len(), face.len(), face.iter().filter(|t| near_points(t)).count());
-    assert!(body_tris >= 2 * face_tris, "the body has other faces: {body_tris} and {face_tris} triangles");
+    // Other faces exist (the flat caps are two triangles each now, so the curved side can be most of the body).
+    assert!(body_tris > face_tris, "the body has other faces: {body_tris} and {face_tris} triangles");
     Cluster { h, many, click, body_tris, face_tris, near_tris }
 }