fix(wipeout): close rectangular fill loop so the mask stops bleeding

The GPU in_polygon ray-cast walks sequential boundary pairs and never
wraps last→first, so it needs an explicit closing vertex. The polygon
fill branch already appends one, but the rectangular branch returned a
bare 4-corner quad — the v3→v0 (left) edge went untested and the solid
mask bled past the boundary. Newly created wipeouts take this branch,
so the fill rendered wider than the clicked box while the border/grips
(drawn as wires) stayed correct. Repeat corner 0 to close the loop.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/scene/mod.rs

@@ -3870,11 +3870,16 @@ impl Scene {
             let vx = (wo.v_vector.x * wo.size.y) as f32;
             let vy = (wo.v_vector.y * wo.size.y) as f32;
             let _ = oz;
+            // Close the loop (repeat corner 0): the GPU `in_polygon` ray-cast
+            // walks sequential vertex pairs and never wraps last→first, so an
+            // unclosed quad leaves the v3→v0 edge untested and the solid mask
+            // bleeds past the boundary — same reason the polygon branch closes.
             vec![
                 [ox, oy],
                 [ox + ux, oy + uy],
                 [ox + ux + vx, oy + uy + vy],
                 [ox + vx, oy + vy],
+                [ox, oy],
             ]
         }
     }