Measure test: the Alt-drag ends within the new 4.5 px snap distance

alt_drag_shows_live_distances_to_the_neighbours dragged the copy to 5 px from the equal-spacing target, which the old 5 px threshold caught and 4.5 does not. The drag now ends at 129 (4 px off); the expected labels are unchanged.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Model-Effort: Opus 5.5 drove and briefed; Sonnet 5.5 wrote at medium

crates/engine/src/measure_tests.rs

@@ -196,9 +196,9 @@ fn alt_drag_shows_live_distances_to_the_neighbours() {
         e
     };
     s.pointer(&ev(PointerKind::Down, 30.0)).unwrap();
-    // Alt duplicates: the copy, dragged to 110..160, snaps to equal spacing between the original
+    // Alt duplicates: the copy, dragged to 109..159, snaps to equal spacing between the original
     // and the other layer (105..155).
-    s.pointer(&ev(PointerKind::Move, 130.0)).unwrap();
+    s.pointer(&ev(PointerKind::Move, 129.0)).unwrap();
     let g = s.tool.overlay.guides.clone();
     assert_eq!(
         labelled(&g),
@@ -209,7 +209,7 @@ fn alt_drag_shows_live_distances_to_the_neighbours() {
             ("45".into(), [155, 50, 200, 50])
         ]
     );
-    s.pointer(&ev(PointerKind::Up, 130.0)).unwrap();
+    s.pointer(&ev(PointerKind::Up, 129.0)).unwrap();
     assert!(s.tool.overlay.guides.is_empty());
 }