ref(container): use only one size for each container

examples/container.zig

@@ -31,6 +31,7 @@ pub fn main() !void {
             .separator = .{ .enabled = false },
         },
         .layout = .{
+            .gap = 2,
             .padding = .all(5),
             .direction = .vertical,
         },
@@ -39,7 +40,7 @@ pub fn main() !void {
         .rectangle = .{ .fill = .blue },
         .layout = .{
             .gap = 1,
-            .direction = .horizontal,
+            .direction = .vertical,
             .padding = .vertical(1),
         },
     });
@@ -54,7 +55,10 @@ pub fn main() !void {
     }));
     try container.append(box);
     try container.append(try App.Container.init(allocator, .{
-        .border = .{ .color = .light_blue, .corners = .squared },
+        .border = .{
+            .color = .light_blue,
+            .sides = .vertical(),
+        },
     }));
     try container.append(try App.Container.init(allocator, .{
         .rectangle = .{ .fill = .blue },