fix: keep HUD balance in endless via invisible moves chip

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/widgets/hud_widget.dart

@@ -16,7 +16,13 @@ class HudWidget extends StatelessWidget {
         Row(
           mainAxisAlignment: MainAxisAlignment.spaceBetween,
           children: [
-            view.endless ? const SizedBox(width: 48) : _movesChip(theme),
+            Visibility(
+              visible: !view.endless,
+              maintainSize: true,
+              maintainAnimation: true,
+              maintainState: true,
+              child: _movesChip(theme),
+            ),
             AnimatedSwitcher(
               duration: const Duration(milliseconds: 200),
               transitionBuilder: (child, anim) =>