fix: avoid child area overflow on split

helix-view/src/tree.rs

@@ -419,10 +419,10 @@ impl Tree {
                                 let mut area = Rect::new(
                                     child_x,
                                     container.area.y,
-                                    width,
+                                    width.saturating_sub(inner_gap),
                                     container.area.height,
                                 );
-                                child_x += width + inner_gap;
+                                child_x += width;
 
                                 // last child takes the remaining width because we can get uneven
                                 // space from rounding