fix(ui): nudge the rack blank star up a pixel

By eye the centred star still read a hair low; subtract 1px from its top
offset (top: calc(0.5% - 1px)).

ui/src/game/Rack.svelte

@@ -139,11 +139,11 @@
     font-weight: 600;
   }
   /* Erudit's blank ("звёздочка") shows its star horizontally centred on the otherwise empty
-     tile face; the small top offset centres its ink against the neighbouring letters' block
-     (it is slightly larger than them so it reads). */
+     tile face; the top offset centres its ink against the neighbouring letters' block, nudged
+     up a pixel to sit right by eye (it is slightly larger than them so it reads). */
   .star {
     position: absolute;
-    top: 0.5%;
+    top: calc(0.5% - 1px);
     left: 0;
     right: 0;
     text-align: center;