Keep static spawn timer for singleplayer games

PR #4198 made the spawn-phase timer count down numSpawnPhaseTurns(), but
singleplayer never adds SpawnTimerExecution (GameRunner.ts), so its spawn
phase doesn't end on a timer — it ends when the player spawns. The
countdown would tick to 0 at ~10s while the phase kept going.

In GameRightSidebar.tick(), restore the old static display (maxTimerValue
* 60, or 0 when unset) during spawn phase for Singleplayer games, leaving
the countdown for all other game types. Uses an explicit gameType check
rather than _isSinglePlayer so replays of multiplayer games still count
down.

src/client/hud/layers/GameRightSidebar.ts

@@ -112,6 +112,16 @@ export class GameRightSidebar extends LitElement implements Controller {
     }
 
     if (this.game.inSpawnPhase()) {
+      // Singleplayer has no spawn timer (SpawnTimerExecution isn't added), so
+      // the spawn phase doesn't count down — keep the old static display.
+      if (this.game.config().gameConfig().gameType === GameType.Singleplayer) {
+        const maxTimerValue = this.game.config().gameConfig().maxTimerValue;
+        this.timer =
+          maxTimerValue !== null && maxTimerValue !== undefined
+            ? maxTimerValue * 60
+            : 0;
+        return;
+      }
       const spawnPhaseDurationTicks = this.game.config().numSpawnPhaseTurns();
       const currentTicks = this.game.ticks();
       const remainingTicks = spawnPhaseDurationTicks - currentTicks;