View tests: the section cap test draws the cap in the cap colour

Since the section hatch per part (#8529), a cut is tinted toward the hatch colour its body's
name picks; Body1 picks the steel one, so the cap test's warm pixels were none
(cpu_picture_section_caps_hide_the_inside). The test turns the part hatch off: it checks that
the cap hides the inside and shows its colour, which the hatch tests cover per part.

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

crates/engine/src/view.rs

@@ -1090,6 +1090,8 @@ mod tests {
             let mut cam = home_camera(&s).unwrap();
             cam.fov = fov;
             let mut sc = scene(&s, &cam).unwrap();
+            // The cap in the cap colour: a part's hatch colour is the one its name picks.
+            sc.part_hatch = None;
             assert!(!section_segments(&s.world_state().unwrap().bodies[0].mesh(), Vec3::new(0.0, 15.0, 0.0), -Vec3::Y).is_empty());
             // A marker inside the body, behind the cut face.
             let red = Rgb(255, 0, 0);