Stretch game state controls across panel

src/styles.css

@@ -86,6 +86,7 @@ button:focus-visible {
   width: 100%;
   display: grid;
   gap: 14px;
+  justify-items: stretch;
 }
 
 .topbar {
@@ -278,6 +279,8 @@ canvas {
 }
 
 .action-group {
+  width: 100%;
+  justify-self: stretch;
   display: grid;
   grid-template-columns: repeat(3, minmax(0, 1fr));
   gap: 8px;