fix(ui): green both lobby scores on a tie, mute a 0:0 board

The lobby tinted only the viewer's own number, and a tie counted as
"leading" — so an even score showed only the viewer's number green,
reading as if the viewer were ahead. A fresh 0:0 board did the same,
accenting the start of a game where nobody has scored.

scoreStanding is now per-seat: the viewer's seat stays green when
leading or tied and red when trailing; an opponent's seat greens only
when it ties the viewer for the lead, so an equal non-zero score paints
both numbers green. When the top score is 0 (nobody has moved) every
number is left muted, like a finished game.

ui/src/screens/Lobby.svelte

@@ -267,11 +267,11 @@
                         {#if badge}<span class="unread-dot" class:nudge={badge === 'nudge'}></span>{/if}
                       </span>
                       <span class="sub scoreline"
-                        >{#each orderedSeats(g) as s, i (s.seat)}{#if i > 0}<span class="sep">{' : '}</span
+                        >{#each orderedSeats(g) as s, i (s.seat)}{@const standing = scoreStanding(g, myId, s)}{#if i > 0}<span class="sep">{' : '}</span
                           >{/if}<span
                             class="num"
-                            class:win={s.accountId === myId && scoreStanding(g, myId) === 'win'}
-                            class:lose={s.accountId === myId && scoreStanding(g, myId) === 'lose'}>{s.score}</span
+                            class:win={standing === 'win'}
+                            class:lose={standing === 'lose'}>{s.score}</span
                           >{/each}</span
                       >
                     </span>
@@ -483,8 +483,9 @@
     font-weight: 700;
     font-size: 0.8rem;
   }
-  /* The viewer's own number on an in-progress game: green when leading or tied, red when
-     losing; other numbers and the separators keep the muted .sub colour. */
+  /* In-progress score colours (see scoreStanding): the viewer's number greens when leading or
+     tied, reds when losing; an opponent's number greens only when it ties the viewer (an equal
+     score paints both green). A fresh 0:0 board and the separators keep the muted .sub colour. */
   .num.win {
     color: var(--ok);
   }